I liked how HL2: EP1 started off right where HL2 ended. It really added to the continuity of the game as opposed to HL1 expansions where you were replaying through the same events just from a different side (Which was still good just not the same). It was also better than the time difference between HL1 and HL2 since you not confused about what has occurred between the 2 games.
It really felt like they trimmed out the fat parts of HL2 and bumped up the action. No long boring sewer section or even vehicle sections (I didn't hate these parts in general in HL2 just the excessive length of them). Just lots of on foot action against the combine and some zombies.
Did find it funny that you start with just the gravity gun and one of the last weapons you get is the crowbar. So it sort of reverses the usual game gun sequence. They also gave me the longer underground subwayish scene I was craving. I also liked the burnt out city scenes you travel through.
Lots of nice action scenes and scripted events. I think I might like it more than HL2 though I wouldn't have wanted to miss HL2. Just combine them together and remove the slow/overly long sections into one more fun game. I still like the City 17 and outside sections more than in the Combine's tower though. Crumbling scifi cities feed my post-apoc love.
Now to finish off my playthrough of the HL series with EP2.