Very nice - but good luck getting restful sleep
This hotel is huge but never really felt over crowded. When we were there in October 2012, they were in the process of renovating a lot of the rooms. We got a newly renovated room and it was very nicely done and very clean. Our room was on a top floor and we had a view of the bay and main pool.
The thing that had me itching to get home to my own bed was that the San Diego Coaster trolley and freight trains blast through the tracks right outside the hotel. It felt like I could hear the bells tinkering for the closing gates over the track every 10 minutes. I was woken up multiple times each and every night to the sound of the track bells. The windows open in the room and I would have loved to have been able to sleep with the windows open but that was impossible with the loud sounds of the train. 
This place had an amazing breakfast buffet every day. It was awesome with everything you could want. Hyatts generally have a good breakfast spread, especially on Sundays, but the Manchester Hyatt did it up every day. 
Expect ridiculous charges for overnight parking, but you do get in-and-out privileges.