I know I'm raising a dead thread here, but I finally made it down to Universal and wanted to weigh in.
The real problem with Rock-It seems to be its unreliability. I was there last week when the park opened and went right to the coaster. Wait time was about 45 minutes and one of the trains wasn't running.
Thought the ride itself was pretty fun. The constantly-moving conveyor-belt station platform was unique but looked as though it probably caused more problems than it solved. I really liked the first loop-heartline roll "double take" element, but other than that it just seemed like a series of low-speed hills and turns hobbled by constant block brakes. I don't think I've ever seen so many brakes on a coaster.
As for the music, my first time riding I used the hidden song function to listen to Zeppelin's "Immigrant Song" and while it synced up pretty well to the lift hill and the first drop, and the coaster in general, I was really disappointed that no effort had been made to edit the songs to better fit the layout of the coaster. I thought that was the whole point of the ride...
Anyway, shortly after getting our one ride in the coaster broke down, and stayed non-functioning well into the afternoon. Just before we left, around 6 a long queue had formed across the astroturf pads in front of the stage outside the entrance to the ride, as the park announced they would be re-opening rock-it. We got back in line, and this time waited about 20 minutes, due to the coaster stopping and starting and now 2 of the trains were being dead-headed. As luck would have it, we managed to board the second-to-last train of the day, as after that the whole attraction went 101 and every car behind the one behind us was empty. I got a lot of dirty looks from all the riders in line behind us in the queue who wouldn't be able to ride that day.
I wasn't willing to fork out the $30 or whatever for the DVD, but I did buy an on-ride photo downstairs at the kiosk under the platform. The dude running it said that this was typical of the ride, and it had been shut down for hours on end practically every day for as long as he had been working there.
All-in-all it's certainly not worth the hype. It reminds me of Eurofighter-type coasters like Mystery Mine or Daredevil Dive, but without the trademark Gerstlauer smoothness. The I-pod stuck into the restraint is hardly a saving grace.
I guess that's what Universal gets for not sticking with Bolliger and Mabillard.