I run Nova Prime on my Motorola Xoom 10.1 tablet and it is nothing but great. It's very fast and pleasantly about. Never had a single glitch or problem with it.
GO Launcher doesn't run quite as well; a few features stalled out, it seemed more ram-piggy, and wasn't as fast as Nova. The Xoom is running on ICS, and I think since GL EX is not created specifically for ICS, it's simply not going to run as well as Nova or Apex, which are ICS specific.
BTW, GL EX runs flawlessly on my Gingerbread Samsung Galaxy Player 5.0, and it's a whale of a blast to use. Ate my life up playing with all those delightful themes!
Now phone-wise, I tried GL EX on Kyocera Rise (ICS), and the HTC Eco V for which I traded the Rise. Same situ as the Xoom; GL EX simply didn't work well for me on these ICS phones. Nova Prime was beautiful on the Rise. I installed Nova Prime on the Evo V, and it seemed ok. But, the Evo began having such issues with dropped calls, failing texts, error messages, that I took it back to bare stock to see if I could stabilize it completely. It's much better but not quite there. I'll try Nova Prime on it again. If it won't run stable and reliably with Nova,I may return it to Radio Shack , gotta be able to trust it.
My experience with GL EX and Gingerbread is excellent and a lot of fun. For ICS, I can really recommend Nova Prime.