I'm considering Hard Rock for 2 nights so I have 3 days of front of the line access, then I'd go over to my DVC in WDW for 4 days and that is is... So 3 in Uni, 4 in WDW... and heck, if I can get a deal for SeaWorld area hotel with SeaWorld tickets, Disney will lose another day from me...
The Hard Rock is great and usually has the middle of the price deals when it comes to the three onsite Universal ones. I really like The Portofino the best. That has some of the best atmosphere I have ever seen in a hotel. Walking around and going to the boats to the parks just blew me away.
The Hard Rock is a close second though. You have a fairly nice pool(although shallow for safety reasons) but the slide is neat and something to show some friends or someone with you...tell them to dunk their head under the water if they had not already. You can hear the same music being pumped in the outside atmosphere speakers under water thanks to some underwater speakers in the pool. Another perk to the hard rock besides the obvious ones is it is a very close walk to the Studios. The closest of the three to the parks in general in my walking experience. I don't even usually wait for the boat whenever I stay at the Hard Rock and am just headed to the studios.