I have stayed in more than 20 places in my many trips to vegas and without a doubt, the Bellagio is by far the best place I have ever stayed. From the rooms, to the views (Make sure you get a fountian view), to the service to the food, it ranks as one of the best, if not the best in Vegas.
Not to mention the first rate poker room.

Of course its not cheap, but in my mind you get what you pay for.

With that being said, I would never stay anywhere other than the host hotel at a convention. Way too many trips back and forth to the room to unload, get and store chips and just unwind with the "splashbar" crowd. The Riv is a far cry from Bellagio, but as far as the convention goes, you wont find me staying anywhere else.

Hope that helps.
Doug