The sound is good with my Takamine GX200. (Yes, Takamine used to make electric guitars). My guitar has the same setup as a Les Paul - two humbuckers, the same bridge configuration, heavy body. I run everything through a Peavy half stack and a Crate mini stack (it was given to me!) I love the noise gate, because I like a lot of distortion, which leads to a lot a noise. The gate takes care of the noise. Now the presets suck. There's just a few cool ones, but none of them have a raw, growling distortion good for thrash metal. I had to program them myself, and succeded quite well too! I finally programed an "early Metallica" sound, but that took me a long time to finally tweak the right controls. You can do it, but be ready for a lot of distortion and compression, which is why you'd need a noise gate!
I'm a big fan of the tube distortions, but lately I've noticed the good quality of the solid state distortions. They're a little muddy on the bottom end, but they do sound good at stage volumes.
I had a problem with distortion just fading away and a high hissing squeal there instead. I was at a gig and I was freaking out. I don't know what it was but it went away before we had to play. During band practice I would notice it on occasion, but after a few minutes, it would just disappear. But it gave me enough of a scare to have some kind of backup. I kept a RAT pedal for "in-case" situations. I never had to use it, but I felt more comfortable knowing I had a back-up distortion.
I've been playing for 12 years, and I'm a big fan of Heavy Metal and Thrash, with some classic rock thrown in. For thrash, I can't get the "perfect" sound, but it's pretty good. For classic rock this is the unit for you. It's easy to use and program, it's got more effects than any other unit I know of. You have to have the right guitar/amp mixture to ge the sound you want. The GSX 2000 is just a preamp. Remember that when tweaking the knobs on your amp.