Lately, I've come to appreciate Voivod's album Dimension Hatross. It's similar to Nothingface, but the production is much warmer, and it is much less experimental. As a whole, Voivod's experimental albums are much better than their early, punky, thrashy albums. They use some really interesting, unorthodox chords, but they make them fit together somehow. This album is definitely what led up to Nothingface. I think it's a loose concept album, but I'll check out the lyrics later, since I'm trying to decipher the music's complexity so far.
I hadn't really gotten into them until now because Voivod is notoriously inconsistent, but at the very least Nothingface and Dimension Hatross are worth hearing. Maybe I'll like the others some, too.
Interestingly, I think fans of old prog, like King Crimson, Yes, and Rush, would enjoy this a lot, probably much more than the typical thrasher. I think much of the criticism of Voivod comes from fans of their earlier, simpler work. Don't let these simians scare you away from some of the best experimental metal of the late 80's.