We are going to IOA and staying at HRH this August for the first time. Here's what I know so far:
We used our Entertainment card and booked our rooms at HRH for $117.50 a night. By staying at HRH, we can use our room keys in IOA for FOTL privileges -- much better than Disney's fastpass from what I understand.
I also read somewhere that we can show our room key at the restaurants on CityWalk and don't have to make reservations -- of course someone can correct me on this one if I'm wrong! I think you need reservations at Emeril's regardless.
The pool at HRH is a somewhat shallow (only 4 feet or something like that) compared to others but from what I read it appears to be well liked by the kids. Apparently there is a slide and you can hear the music under the water.
The rooms at HRH are a little smaller than PBH. PBH has a more relaxing feel -- HRH is simply-stated the Hard Rock Hotel...its all in the name.
So, that's all I know so far. Of course I could be forgetting something and I actually have never been there! Just watch these boards -- You'll find out all you need to know eventually!
Good Luck!