I play either a Gibson Les Paul or a USA strat though a Fender Roc-Pro amp (which I don't like much but that's a different story). Engaging the pedal produces quite a bit of hum, especially on the strat, but that's the nature of the beast. I haven't tried it, but perhaps a noise gate would cut out a lot of that. The Big Muff produces one of the most in-your-face sounds of any pedal ever made, so if you're looking to create a jet-engine roar with your guitar, this pedal works perfectly. I find it's best for power chords, double-stops, or solo stuff. Rolling the sustain (ie distortion) all the way back will give you a fuzzy sounding overdrive, which I like, but can still make chords more complex than power chords sound a tad muddy. Maxing out the sustain really allows you to hold notes forever, especially with humbuckers. My Gibson weighs a ton - its natural sustain coupled with this pedal will create sound that sustains as long as I fret the string. The tone knob has a huge range, from trebly hive-of-bees buzz to bowel rattling roar. Fiddling with the knobs will get you a range of sound anywhere from Smashing Pumpkins to Hendrix. I never try to exactly emulate anyone's sound, but you can get pretty close by just casually messing around with this pedal.
The pedal doesn't have true bypass, but I play noisy rock anyway and don't really care.
Mine's over 10 years old and the only thing wrong with it is the pots are a bit scratchy. It has the 'cheap' plastic inputs, but I've never had a problem with them. I worry about the wires that attach to the battery breaking, so I'm careful when I change the 9V, but nothing bad has happened yet.
This is my favorite pedal, and I use it in almost everything I write, which, again, is loud rock n roll. I've been playing about 20 years. Sometimes kind of country, sometimes kind of punk, sometimes kinda metal, sometimes kind of ambient. I'd be obligated to replace it if something happened to it. I got this when I was a noob and didn't realize there were different models of Big Muffs, but I don't regret it. I love the sound of this thing, and having compared it to a handful of other fuzzes, I still love it. On my wishlist would be inputs in the right places, not so damn big, visible position markers on the pots (mine is old and has nearly invisible divots on the knobs), and true bypass. And better clarity on high strings would be great.