Unfortunately there are not too many options in New Haven for higher end hotels, so the Omni is one of very few options in the center of town. I have stayed here several times and found a large difference in the experience based on the room. The last stay in a corner room was very nice, the bathroom appears to have been slightly updated and the normally noisy heater / air conditioner was not as bad as in the others, and the room was larger. Which is to say that in the other rooms, the rooms were small, bathroom in need of renovation and so forth.
They seem to be doing some work on the building renovating the restaurant / retail space on the street level and there may be some good options moving in, but for now it is mostly space available signs, but no matter because as they say location, location, location - and this hotel has it. There are many small and good restaurants near by with options that will meet any need you have within easy walking distance.
Because there are not that many options in the center of New Haven I have found that the hotel is completely booked when there are any University events, so if you are coming for one you really need to book early. It isn't a great hotel, that is partially due to the aging building but the staff is pleasant enough in a very busy place, and did I mention location, location, location?