On guitar (through a bass amp, so a slightly different perspective), the pedal is great. Its been summed up pretty well by everyone else... cleans up with a light touch or volume knob, nice gritty mids that are pleasantly adjustable to taste and a bit dark. I'm not much of a guitarist, and haven't used a hiwatt, so I'll leave that part of the reveiw to eveyone else. The main thing that stands out to me that I haven't read before is, it reminds me of a dialed back fuzz more than a distortion. I can't quite put my finger on why, but with the gain cranked (or a boost in front) that's just kinda the feeling I get from it.
And, because its a little unusual, here's the test rig (plus a solid state bass amp and a 112 cab).
On bass, my thought's have changed a bit more since the first impressions. The lows come off a lot more at higher volumes, but its holds up better than lots of mid-high gain pedals with the tone below 12 o'clock. Like I said the last time, its not an unnatural kinda rolloff... so it doesn't seem too weird. I picked up a parallel blend pedal recently, and with some clean mixed in to bring the bottom back up the pedal definately lost some of the magic that it has in the mids. Sounded great, and as a bassist looking for a grinding distortion and not trying to get a hiwatt sound I loved it... but thats clearly not the goal of the pedal so I'm happy putting it in a loop if I need too. Its still the best gritty drive/distortion I've found, although the blueberry with a boost can come close in a pinch.
Overall, personal highlights are that the mids let it stand out but it doesn't ever really get harsh, and that it retains a lot of the character of your guitar until the gain is really cranked. The biggest con I can find is that I'm having a rough time stacking it with my fuzz pedals. I can't get a good sound running a fuzz into the H. Lots of people on here have said they love it with a fuzz first, but I usually end up with something sputtery and way too muffled and give up. I could be doing something wrong, but I can't really figure what or why this one setup would be off. It runs fine before a fuzz or overdrive, and takes a mid scoop (from my amp... about 400Hz) really well for some different textures. I get good sounds with modulation or filter pedals before or after, its just the fuzz pedals that are giving me trouble...
So, in the end, I doubt it'll ever bump my blueberry or just slide into a spot on my main board, but I'm thinking a simple board with a boost/cut style volume pedal up front and an EQ after now and then would be a good change.