Well, as far as interactivity of objects, Bloodlines isn't even close to HL2.
The cool part is the character animation. They put all their effort into the NPC dialogs. I'm sure you've seen the movies of where it does a closeup on peoples faces?
Really really good stuff. Occasionally I'll get freaked out because some NPC will remind me of a real person I know. They did all the facial animation quite well.. and the way source lipsyncs automagically is quite nifty.
There were a few long NPC dialoges that I loaded up a few times just to make sure I didn't miss something nifty.
Combat is really stunted. I would not go into this thinking you're going to get HL2 style combat.
The story and characters is where this game is going... not massive combat.