It's a 4 star hotel, the location is great but there are a lot of 4-5 hotels in the area. I choose it according to the photos they put on the websites, and the photos here on TripAdvisor.
The Room was very small, and looked nothing like the picture. there was no bath, only a shower - and very small one. The chair was broken. I asked to change rooms, the front desk was unfriendly about it. as I used the soap in the room, I wasn't able to change rooms anymore for that night (as there was no one to clean after me), even not for a surcharge. As he was alone in the hotel - he couldn't help with any problem outside his post, so he couldn't get me another chair. The hair blower didn't work as well.
On the second day I could change rooms (had to pay 33% surcharge, but thats fine...). The executive room was well equipped and nicely furnished, the bathroom was very nice also (this is the room they have on their site). The phone didn't work well though...
Breakfast was nice, don't expect vegetables or scrambled eggs, there is also nobody in sight - one should go to reception.

All in all - not a good experience, I don't recommend it...

I was in Amsterdam for a conference. The Delphi was a pleasant 15 minute walk from the RAI conference center. My wife accompanied me and hooked up with several other wives from the conference. We had a recently refurbished room on the second (European) floor with a shared balcony facing the courtyard. We saw up to four ringed parakeets at a time visiting a feeder at the apartment next door. We arrived at 9 AM and were given a room immediately. We were even treated to breakfast when we arrived. The breakfast room doubles as a bar for guests in the evenings, although is not used much. Just ask the desk clerk for drinks and he/she will take care of it. One night two fellows walked in the door and asked for drinks. The clerk asked if they were guests and they said yes. Then he requested their room numbers which they gave. He pointed out that the hotel had no rooms with those numbers and asked them to leave.

We slept most evenings with the windows open, closing them at 7AM when the early flights began arriving at Schiphol. The room was clean, housekeeping was efficient, and staff was helpful and friendly. Breakfast was good, but unvarying over the nine mornings we were there.

There are several good restaurants (mostly Italian) and shops on Bethovenstraat. However, I highly recommend La Falote, a little neighborhood restaurant run by Chef Peter Linden in the opposite direction. Walk past the tram stop and follow the main street until it comes to a T. Cross to the right and it is about 1/2 block on the right, about a 10 minute walk from the hotel. (Making a left at the T takes you to the museums). There is a Dag (daily) Menu for 10 euros. Chef Linden is young and very gregarious, hauling out his accordion both nights we visited. He also discourages smoking. Good, solid food with a local flavor.

One negative comment. I discovered that the room safe was not fastened to anything. Maintenance did not get around to correcting the matter during my visit.

We liked this hotel and would definitely stay again.

We stayed 4 nights at the Delphi and and found it to be a great accomadation for our needs. The room was ample in size, the breakfasts sufficient and it was only a 2 minute walk to a tram stop that took us right into the city center (10-15 minutes). The hotel is outside of the city center in a very quiet neighborhood. From the hotel you could easily walk to the museum area. The people that work here are very friendly and helpful. We arrived at the hotel at 8am after a red-eye from L.A. and were, of course, exhausted. The receptionist told us that the room was not quite ready and offered us breakfast while we waited about about an hour for our room. As soon as the room was ready we were notified and we were in our room by 9am. In the area there are a couple of small stores and restaurants if you are not in the mood to deal with the city.

A little warning for those individuals who are not interested only in the red light district and the "coffeeshops!" Many of the museums and other sights are closed or have restricted access because of renovations until 2009. Thought we had plenty to do for the 4 days we were there, we were disappointed.

Having spent a while prevaricating over hotel choice, we plumped for the Delphi as it seemd to have the right balance between price and other reviewers' ratings. We arrived really late after several hours delay courtesy of UK snow. We were let in by a rather surly nightdesk attendant, who carried out his tasks in a perfunctory manner. Thereafter, things were fairly smooth.
We had two twin rooms, both a decent size, particularly for Amsterdam. Both had decent sized bathrooms which left me puzzled as to why both had toilets which required at least one of your legs to be contorted somewhat unnaturally. I thought it was just me- six feet four tall- but all of my family had the same problem.
Breakfast was OK- by day 4 the rather limited choice meant the original 'delight' was wearing somewhat thin.
All this seems rather churlish, but there are many good points. The hotel is 2 minutes away from the number 5 tram, most tourist sites are really easily accessed. Overall, the staff were really pleasant and helpful. Housekeeping were efficient and unobtrusive. Fresh coffee and tea (complimentary) rather than rehydrating old packets in your room made a pleasant change.
My only word of caution- don't let your kids flick through the TV channels- the adverts for the adult films are extremely graphic!