That Eggs and Sausage demo is pretty cool, I like the album version better, but I love the whole poetry and snaps instrumentation.
I know there are a ton of Nirvana demos out because they want to milk as much money out of Kurt Cobain as possible. Here are some interesting ones.
I actually like this version a lot better than the other versions. It has a unique, 60s and CCR kind of vibe.
This is really only interesting because he says "Yeah Hey" instead of "Yeah Yeah"
EDIT: This is a good example of a demo that's significantly better than the album version. This version of "Can't Hardly Wait" by The Replacements has all the grit and attitude that was lacking from the eventual album version. It's not really lo-fi or anything, but I have no idea why this version of the song wasn't good enough to put on Tim.