Rhymesayers is supposed to be reissuing it this year.
I don't know if it's DOOM's strongest effort, but it's the most album that's him - him producing, him rapping, etc. It's really a collection of singles from 1997 to 1999 (the Sub Verse reissue would be to 2001, since it includes his verse from "Voices").
"Dead Bent" and "?" are two of my favorite hip-hop songs ever. The MF Grimm solo, "Tick, Tock" > the entire Grey Album.