The more like the original, the better for me and it seems most other people would be happy with just a visual update and a new Sp story, I get really fustrated with the recent trend to add super sized - end game units. I know why they include them, but I prefer fighting it out with normal units and taking the time to win properly. It's not like MP games of starcraft go on for ever, infact allot of matches are over in 20 mins or less.
I'm excited to see what new units they add, but i'd love it done in a Broodwar way, add but don't go silly and break the game.
Blizzard know what they are doing, I have complete faith in them to get SC2 out and really fun. I would say there is no developer out where who I trust more to release the game when it's really ready. (Ok maybe Valve and don't mention WoW launch as a bad example of releasing a game early, MMO's are different thing all together)