I bought a GT-6B in December and haven't stopped using it since...some of my likes:
1. Compressor: 2 of them are not useful. The two that are are wonderful and easily dialed in. Best of all they are "musical"
2. The Ampeg model: Is sweet sounding, and when you turn up the gain and turn the level down...well, you guys know what should happen and it does...think Noel's fuzz line on Dolly Dagger.
3. The Effects: Chorus (Particularly the 2x2 using the stereo outs), "Muff Fuzz", Reverb & Delay (I'm still stumped at how to get the tap tempo working) and the Octave modes track really well and can be configured to work similar to a Whammy pedal...cool stuff.
Also I am a hardcore knob tweaker. This thing is paradise!!!


Everything in here can be messed with.
Finally it has not only stereo amp outputs but stereo XLR as well...In addition to MIDI and Digital outs too!!!
Dislikes:
All the presets except "Geddy". Other than that...all of them.
The B15 model. If your sound needs this amp model, don't get the GT-6B. It fuzzes out with the gain on 3.
The looper could have more time but I own and use a Jamman. Best 300 I ever spent was on that Digitech unit, so i didnt buy the Boss for looping. However, If your only looping is done in short live bursts via DL-4, Headrush and such you could find it useful...
And lastly, no USB out. It is nice to have midi though...
Overall a great unit...
It'll hold off my GT-10B GAS for a while...
And I only paid 250...New!!!