Well, that does indeed look like a DOD Grunge pedal. If this is, and that's what it looks like, then perhaps this is why Kurt sarcastically clapped to the crowd after the concert: "You people can't tell the difference!" I've always wondered why he did that. In the full length video, he kind of goes back and forth with a couple people in the crowd, so that could be it too. But I digress.
I have a DOD FX86 Deathmetal, and it is pretty hard to get a decent sounding tone out of the thing. I found something of a sweet spot on it, though. But It's hard to keep it from sounding like, well, death metal.
Never tried a DOD Grunge, but I imagine a lot of people have been duped into thinking that thing captures the Nirvana sound. I've found that a good amp and pickups can work wonders with nearly any pedal.