My wife and I stayed here for 3 days recently for a brief vacation to unwind and not have to worry about, really, anything.   The Don Cesar was up to the task. 
Staff was very friendly and accommodating of requests.  We did self park, which was honestly fine, the lot is right across the street. The lobby bartenders were engaging and friendly, and mixed up some great drinks on our first night. 
We cannot speak for all the restaurants onsite, as we only ate breakfast and dinner once while at the hotel (both at the casual restaurant).  The food was good but not incredibly memorable. We wanted to explore other options in St Pete for food. 
Our room was a corner King with a balcony facing the bay.  The room, while not huge, was perfectly spacious for two adults and clean. The A/C worked well, although as others have noticed, it is a bit on the noisier side, if that bothers you (it does not bother me, I just want a cool room).  Since it is an old hotel, the bathrooms are quaint, but this was not an issue for us. They were clean and well stocked. Turndown service was a nice touch.
The first day we spent on the beach, and this was a great experience, as the hotel staff on the beach sets you up with chairs and towels, and the staff walks the beach with food and drink service. The second day we spent at the pool.  No complaints, the pool temp was perfect, plenty of servers checking on you, ample towels, and tasteful DJ music.  
We did not use the Spa, but the fitness center was clean and had plenty of machines and weights available. 
In general, it was a pricey visit, but the service was top notch and the hotel and grounds are beautiful. They are doing some renovation work still, possibly from last year's hurricane, but it wasn't an issue.  Some families with younger kids present, but in general it was definitely an adult-oriented place, which was what we wanted.
We would recommend!