I run a Godin LGT with 2 single coils and a Seymour Duncan humbucker into it. Sounds very clear, has about the best definition of any amp I've played. My music style is sort of a mix of butt rock, metal, some J-rock, and hardcore. It suits any style pretty well though, and the definition and high gain settings particularly suit metal and rock playing. The amp is not noisy at all, thanks to the noise gate. However, if you turn it off it is as noisy as any tube amp out there. You pretty much HAVE to turn on the noise gate, which seems odd since I never had to get a gate for the Mesa Boogie DC-3 I used to have. So that's sort of an odd point. But the sound quality doesn't seem to suffer much. Nearly all of the amp models are useful, and I've found that it behaves like the tube amps I've played, a very Overdrive sound. The Rectifier, in particuler sounds good, and I'm pretty familiar with Mesa Boogie sounds; a very accurate model. The stomp box models are pretty crappy though, and it seems odd that you don't get to turn a tone knob, it has like 3 preset sounds in it for each box, ALL of which sound like crap. The octaver is sort of okay though, but doesn't sound too musical to me. The speaker cabs are pretty cool, but only about 2 or 3 of them sound clear enough for practical use, I recommend turning them off unless you are looking for the amp-specific sound. Even so, be prepared to tweak for hours. The chorus and delay effects are the freakin' BEST I'VE EVER HEARD or used. There's no shortage of sounds you can make with them. I would have liked to soon a loop thing built into this amp, instead of the crappy ring modulator, but I really can't complain about these effects. The stereo delays are unreal for being built-in, and sound better than any stomp box I've used or tried out, no signal distortion or anything. The reverb model is okay, but I don't use much reverb in my style, since I like as clear, defined sound as possible. By far the best thing in this whole amp, though, is the 5-band EQ. After the DC-3, I can't accept an amp that doesn't have one, and the Line 6 one is just as good, if not better. You simply have no limit to your amp sound, whether you like snarly treble distortion (like me), or metal mid-scooping brutality (like every other unoriginal neanderthal (I mean you DISTURBED, etc.) with a guitar).
The Clean sounds are top-notch. They get loud without getting harsh. Go down like BUTTA. Impressively comparable to some Fender amps' clean channels. One bad thing though, you get a crazy, LOUD, POING! sound when you switch patches that have delay on and off, though there is a way to get around this if you read the manual.
I can't quote on this since I haven't had mine for too long. But my friend's amp is standing up and he gigs with it all the time and isn't as nice to it (the thing weighs frickin' 70 lbs.) as I am but it takes the punishment and still performs. The heat sinks, like all computer based equipment don't look so good though, but they seem to do their job fine.
WARNING! The Line 6 Floorboard is a piece of frickin' !@#$!@#$!@#$!@#$!@#$!@#$!@#$!@#$^$^@#$. NEVER buy this thing, it's totally unreliable. Practically everyone that owns one that I know or have heard of has the thing break down on them. I even busted a knob and one expression pedal just trying it out at Guitar Center and I wasn't screwing around or anything. The FB is also unconscionably expensive at $200-300. The wannabe USB port it connects with is lame, but not as lame as the cable that comes with it that frays at the connector, exposing the wires no matter how nice you are to it. I mean, DEAR GOD, what were they THINKING? Who built it? Keebler elves? I use a Behringer FCB-1010 for mine and it works just as well and much more reliably. If I rate the L6 Floorboard it gets a 2 or 3.
I've been playing for more than 6 years. I also own the Line 6 Chorus modeller rack, and the aforementioned POD 2.0 and Behringer FCB-1010. In addition I use the excellent MosValve 962 power amp to boost my AX2's signal into a 4x12 cab so I don't get the AX2 too hot, though I probably don't need to do this. It does allow me to use my BBE though.
I would buy this amp again if it were stolen, unless I could get a Vetta instead for a similar price. I love the excellent sounds and variety, I hate the proprietary stuff and lack of effects loop. All in all, if you can find one used, you've got the best thing going to sound great without being bankrolled by a record label.