I think that he's a nasty kind of guy, but not bad such as evil... he's the kind of guy who you always suspect to be the evil one, but really isn't...
And about the apperating thing.. well, Snape wasn't there for a time, now was he... I looked up the 4th book again, and it says that 'Hagrid, Professor Moody, Prof, McGonagall and Prof Flitwick' were the ones walking around the maze with the red stars and stuff. Note, Prof Snape wasn't there... he could have cought a taxi, or the wizarding equilivant, to somewhere in which he coud apperate and yeah... provided that he knew about Voldie coming back beforehand... hrmm, seeming much less likely now, isnt' it...
Oh wells, I never really believed this theory anyways, just thought it interesting to speculate over!!!
