I've been a fan of the Age of Empires series, and when I play Starcraft it seems very slow. However, I'm told that most Starcraft games last a few hours unless you're on a money map. Most AoE games last 20 minutes to one hour.
One criticism that I've heard of the Starcraft II game is that most of the units are "glass cannons" -- meaning that they all do lots of damage but have little hitpoints, compared to the original Starcraft.
However, since I haven't played Starcraft much, I wouldn't really be able to give a good opinion on the new game. However, I'm looking forward to seeing the new Starcraft since the original Starcraft was wildly popular, and I'd like to be able to try an up-to-date version of it.