Flying to DIA, I made online reservation with Big Sky Shuttle for both my trip into downtown Denver and my return trip to DIA.
No problems, so I can recommend this shuttle company.

My check in was early, so my one bedroom suite was not ready so they offered me a studio on the top floor. Check in was friendly and welcoming. Sometimes the studio appear to be roomier because there is not that wall separating the bedroom from rest of the suite. This property is relatively new so everything looks good. The room was very clean and cleaned well each day I was there. Good size studio room was small kitchen, with breakfast nook. Small loveseat and lounge chair but in a fun positon. There was plenty of natural light in this room. Overlooking the courtyard. Bathroom was clean and water pressure was good and temperature was good.

My room was quiet and the bed was comfortable. The A.C worked well but was a bit noisy. The Residence Inn breakfast was better than most Residence Inns and there was plenty of room to sit and eat as well plenty of friendly staff helping around for the breakfast.

In the large lobby there are also two complimentary computer/internet stations. There is small gym with Precor machines and outside of the gym is a patio which features a hotub. Lots of smoking folks hang out there.

This property is just a few blocks from the 16th street mall. If you're reasonably good shape you can also walk to Coor's Field from this property.

The 16th Street mall, like some of the other reviewers have stated is nothing unique. Though there are plenty of souvenirs vendors located there and there are you're typical shops and restaurants you find in most cities. There are a fair number of street people around the open mall and some do ask for some change.

There is a free bus that goes in both directions of the mall.
At one end is the local and state govenment facilities and just a few streets from there down is the famous and historic Brown hotel (Where Obama and Clinton are staying for the DCC.

At the other end of the mall is Union Station and there are some good resturants down. Like the Wynkomp Brewing Company, towards Coors Field. Also further down from Union Station, a little bit of a walk of Convergence Park. A nice water park with a massive REI store there.

I found the small but more unique Larimer Square more interesting than the 16th Street Mall. There is great coffee house there called the Market.

The convention center is walkable from the City Center Residence Inn. On the 16th street mall are several convenience stores nearby: 7-11, Rite Aid and Walgreens.

I took the Grayline City tour. My morning tour was cancelled because according to Grayline the bus driver called in sick.
So I took the afternoon tour. The tour bus can pick you up at your hotel if you call in advance. The bus then goes to the Cherry Creek Shop center (typical suburban upscale mall).

The tour is not too interesting other than it gives you a good point of reference of how close many of the Denver offerings are from each other and accessible by light rain or bus. With Denver's very good public transportation system you get easily get to it's many sporting venues: Invesco Field at Mile High, the Pepsi Center and Coor's Field.

There is huge condo buidling boom in downtown Denver, kinda of like downtown Seattle.

The weather in Denver was not too hot and plesant for August.
Many of the downtown eating establishment like Zeidy's Deli close during the weekend and primary cater to the downtown working commuters.

My stay at the Residence Inn City Center was pleasant and Icannot think of any problems. I highly recommend this property if you need a base of operations and/or your business is downtown. A clean and modern facility with great staff and great location.

We want to join the many travelers who stayed at the Residence Inn City Center in Denver. We were so very surprised that this hotel was more than we expected and at a very reasonable price. We got more for our money here for sure than some of the $400 a night hotels in Seattle. The manager on duty was exceptional!

Trip Summary:

Length of Stay - 4 nights each x 2 visits
Room Class Booked - Standard Non-Smoking
Room Class Stayed - Standard Non-Smoking
Rate Class (with Taxes): $140 - Corporate Rate - Rack is $300. Still a good value at rack rate.

Check-In:

Arrived about 9 PM via taxi - the check in desk was not busy and well staffed. The desk clerk was extremely nice and had me checked in promptly, inquiring if I needed a wakeup call.

Room:

Like most residence in 1 bedrooms, the mini-suite consists of a sitting area/dining area/work area/kitchen space of decent size. The bedroom contained 1 queen size bed, and while a little smaller than at some RIs I have stayed in, was more than spacious. A full sized vanity area is adjacent to the bathroom.

The rooms are well maintained and were cleaned spotlessly each day. Several times, the housekeeper left a nice note. I travel with a stuffed animal my wife gave me when we were dating, on a couple of occasions he was posed in the room. Fresh toiletries were left, partials were not removed (I view this as a good thing, taking them before used up is just a waste.)

Amenities:

If I had one negative, it would be the lack of a pool. There is a 24 hour outdoor hot tub and a decent workout room. The TV offers a full suite of cable channels. There is 'The Market' in the lobby which sells a selection of snacks and RTE meals at reasonable prices.

Food and Beverage:

Each day, the hotel offers a free breakfast in the Hearth Room in the lobby. It's a huge spread, varies daily, but for example today featured scrambled eggs, ham and cheese scrambled eggs, bacon, potatoes, sausage, biscuits, fruit salad, 3 kinds of cold cereals, make it yourself waffles and french toast. Plus the usual breads and juices....

Monday thru Thursday evenings, there is a free reception in the Hearth Room. Not just snacks, these are full meal offerings. The menu changes regularly, but for example one night this week featured Mac and Cheese (with sliced hotdog option), 2 types of salad, fresh baked whole wheat roles, and vegetarian tomato tortellini soup. There is a cash bar available in the evenings.

Room service is available from the Broker restaurant next door (at comparable prices to the establishment). I didn't use room service this trip, see Location, below.

Location:

The hotel is located less than a 2 block walk from the 16th street mall, a pedestrian walkway over 1 mile long and featuring a huge assortment of shops and restaurants, both local and chain (hence no room service). A free shuttle bus runs the length of the mall and makes it easy to get to the LoDo section in a quick amount of time.

Coors field is about a 15 minute walk (perfectly safe both ways, I did it for a game).

The hotel is also convenient to many businesses, and by taking advantage of the mall shuttle, less than a 15 minute trip to the Pepsi center.

Customer service:

The hotel staff is really top notch and seems to enjoy working at the hotel. One night, the AC in the room made a slight rattling noise. I reported the issue to the front desk in the AM, and the problem was resolved prior to my return to the room. There was a message on the phone indicating the problem had been resolved, and a note in the room from maintenance to let me know they had been there, as they had to move my suitcase.

Hearth room staff kept the tables constantly clean.

Other Notes:

On some nights, the hotel offers bingo tournaments for charity, or other events in the hearth room.

Conclusion:

This is one of the top Residence Inns I have stayed at (and I have stayed at more than a few. I cannot recommend it enough for either a short or long stay in the Denver area.

I'm a Marriott Rewards member so I've been to a lot of Marriott Properties. This property is 2 blocks away from 16th street pedestrian mall. We were just at Sheraton Denver which is right on 16th street but that property was too big that you felt lost and on your own (room were also old) . This property is new (cleaner) and staff are friendly. Free breakfast (supplied well, unlike other properties when food run out fast), wifi, and happy hour. Parking is $13 (in/out privilege) which isn't bad since across the street public parking is $8 (till 6am only). I would definitely recommend this to friends. I used my reward points to stay here so it was a pleasant surprise that we were also given a nice room without asking (typically they give you poorly located room when using points). It was hard to book here because a month ago it was sold out but I called again a week prior to coming and was happy to find out that I could stay during the dates I needed.