I stayed at the Riverwalk last week as well, and got a two-room suite on the fifth floor (I'm 100% on at least a junior-type suite upgrade in four stays there). The front desk was generally courteous, and the valets were very quick.
That said, I also experienced some of the OP's problems. The hot water system did have its hiccups, and the elevators are probably one of the slowest (if not the slowest) I've ever seen in a hotel. The rooms are slightly shabby IMO, as well. And for the first three stays, I didn't get my suite upgrades until I asked.
Overall, it seems that this hotel has a very high occupancy rate because of its location, so I guess there's not much incentive for any major improvements. I'm guessing the Westin Harbour Island is probably the best SPG hotel in Tampa (though I haven't stayed there).
P.S. Doing my expense report right now, and the charge still shows up on my corporate card statement as "RADISSON RIVERWALK HOTEL."
