I'm using this with a Marshall rack mount stereo amp (if you've heard what the GSP 5 sounds like in stereo, you'll never go back to mono again) and two ADA speaker cabs. The sounds are absolutely awesome. I've been playing for almost 30 years and I've never heard anything like this thing. Last year I thought with the new technology I would be able to get something better so I tried out a bunch of different processors like for example an RP7 which I spent weeks tweaking and programming but nothing can still touch the sound I get out of the GSP 5. When I play live gigs I always get other guitar players come and ask me how on earth I get such a great sound (even guys that own GSP 2112's and Mesa Boogies!). There are two major drawbacks with this processor, otherwise it would be absolutely perfect. First: when playing with distortion and certain chorus effects, it is extremely NOISY. I had to get an Alesis noise-gate to deal with that. Second: The sound level (volume) for a program goes up or down in STEPS. That means a lot of times it is either too loud or too soft, unless you tweak the master volume. The distortion sounds are excellent for being digital, I son't care what anybody else says. I get a powerful, crunchy distortion for rythm sounds (I play mostly Rock and Blues)as well as some great lead sounds (my favorites are the 'Lukather Grease' preset as well as a gated-reverb sound that, with maximum distortion, makes the guitar sing like Santana's. Come to think of it, maybe ther's a third shortcoming: no compression/sustain. I don't need one for the distorted sounds (just turn op the amount af distortion), but for the clean sounds I've had to add a sustain pedal.
Bought it new, had it for 10 years, never had a problem (even still has the original battery). Used it for 10 years without a backup, trust it completely.
I play Classic rock and Blues, and this is perfect for me, only wish it was less noisy and had 'stepless' volume control for program sounds. I've been playing guitar for 30 years. I own a Mexican Strat with Seymour Duncan hotrails in the bridge position and a Squier fat strat. If it were stolen, I'd probably get another one. I love its sound, I hate the noise + the irritating volume programming. I actually chose this processor in '91 because it was the cheapest one I could get, although even then I thought it sounded better than anything else out there, and it still does.