I booked a room for one night (Fri night in July) on the hotel's website for a "leisure night" package. This includes valet parking in the price, for $159. A tip on using the website: make sure to view all prices available instead of immediately booking the first one that pops up; they seem to push the more expensive package instead of the best deal.
Hotel Service: Overall, friendly and polite. Nothing to write home about, but staff definitely put in effort to be professional. My biggest gripe was the constant error of the hotel charging me for valet parking, which was approx $30. I had to correct the front desk when I arrived and I also had to have them remove it again from the charge at the end of my stay. I would recommend reviewing your bill carefully.
Hotel Location: The best aspect of this hotel was definitely its location. In addition to being a block away from all of the touristy spots (Liberty Bell, Independence Park, Visitor's Center, etc), it was so close to the better restaurants and bars in Philly. If you walk along Chestnut or Market St down towards the river, you will encounter so many greats restaurants and bars along the way, such as Buddakan, Fork, Amada, Farmacia, Dolce, Bijou. We had a solid meal at Haru on 3rd and Chestnut (it's a Japanese restaurant chain in NYC, but it was significantly nicer and better in Philly). At night, there's tons of people spilling out on the streets from all the bars, clubs and lounges, all within walking distance from the hotel. It was a nice change to see Philly transform from a family destination during the day to the upbeat nightlife of the younger college students and professionals. In addition, a nice long walk to Jim's Steaks (walk along 4th down to South St) is a MUST! It's the only place I will go to for cheesesteaks. However, the line was over an hour long on Saturday afternoon!
Hotel Parking: Though parking is expensive, I would recommend leaving your car in a garage. I believe there are garages nearby that are cheaper than the hotel's rate of approx $30 for valet and $24 for self-parking. You do not need to use your car. We took advantage of the valet parking and constantly drove everywhere, esp since it was so hot, but it really wasn't necessary b/c many points of interest were within walking distance, there were many trolleys, shuttles, buses and public transportation nearby.
Hotel Room: We had a room on the 3rd floor facing Chestnut Street, the front of the hotel. Since it was nearly 100 degrees when we were in Philly, we did not open the windows and did not hear any noise from outside. We actually liked having the room facing the front b/c we were able to peer down and see if our car was brought out to the front. The room was bigger than the room we stayed in at an earlier trip to the Sofitel in Rittenhouse Square. Also, they must've updated their TVs b/c there was a huge plasma TV plastered to the wall. The only annoying aspect was that the TV did not swivel to face the bed, so it's off to the side of the bed and the channel offerings were very, very basic (with HBO). Otherwise, I was quite pleased with it. The bathroom was spacious and clean, despite being a bit dated. There was no sign of significant wear and tear. The free wireless internet service was fast, reliable and great.
As I mentioned previously, I had stayed at the Sofitel before, which is down on 17th St by Rittenhouse Square. The area around there is definitely quieter and more conservative. There were many cute stores and restaurants in that area as well, but as a young professional I really enjoyed being close to the hustle and bustle of Old/Center City. Plus, there was no free wireless internet in the hotel rooms in Sofitel, which was a definite negative for me.
Overall, though the hotel was not the most stellar hotel I've been to, the location of Omni is what gives this place 4 stars, despite the minor gripes I had along the way. I'd recommend staying here over Sofitel, despite the fact that the hotel room was overall nicer at the Sofitel. It's all about the location.