Guitar Suite

If you're looking for good basic effects to use with guitar, this is where you should start. Of course, they are also great "character" effects to use with other instruments.
It's hard not to be skeptical of the rather silly promo blurb, and I wouldn't necessarily swear that they're perfect emulations of the specific products listed, but they really do do a good job of capturing the sounds of the 8 pedals & 2 amps.

Anyway, free.
Interface: There is none, but you really don't need one.
Sound: Very good.
Features: Same as the hardware. It's too bad they're mono only, but of course, so is the hardware.
Docs: essentially nothing more than you see listed in the "more information" above
Presets: none, but again, not really needed and it's not like the hardware has them.
Customer support: no idea.
VFM: 10, of course
Stability: no probs with me.