I have a carvin Legacy head and our bass player has the Carvin "Red Eye" head and two carvin basses.
I love my Legacy. Built very well. I had one problem with it, the volume would drop at strange times, then it gave me a funky noise. I thought that it might be something big, but it turned out to be power tube failure. Replaced those and it was good as new again. As for the tone, it's great. Very liquidy lead tones, articulate, but thick; similar to a Mesa Mark series in "feel and response", but more mid range crunch to it and not as saturated. The cleans are amazing, they do sound just like Vai's clean stuff. The distorted tones aren't quite Vai's sound, but I think that is the DS-1 and the TC Gforce.
I think that they are very good for the cost to product ratio...resale value isn't the best, so buy used!