Yeah, the scripted events are awesome and I like that I still have control over the game when they happen. I think half-life games are the most immersive games I've ever played.

Lost Coast is just a small little area designed to showcase the game's graphics. There's a few dudes to shoot (if I remember correctly) and an integrated commentary, but not much else.  
 
HL2 was really good at immersing you in the character, for the reasons you stated. The camera is never really pulled away from you (if at all), so everything unfolds before your eyes, so to speak.

Half Life: The Lost Coast is just a tech demo. Not a full game.

I began playing Half Life Episode 2 yesterday.  While it seems quite good, and the story took an impressive and unexpected turn, it still kinda creeps me out having to walk through those tunnels with all those grubs.
 
I think one of the most amazing aspects of Half Life (any Half Life game) is the scripted events that are not limited by your perspective.  Anyone who has played even the beginning of Half Life knows there are moments when things are happening around you, but you are able to look and move around, giving you the feeling those events are happening spontaneously, while avoiding relying on things like FMV (Full Motion Video - i.e. cut scenes) which may detract from your sense of really being in the game.

I don't know if I will have time to play anything else before Duke Nukem Forever is released, but I am still considering picking up Portal 2 and even Borderlands.
 
I noticed I also have a copy of Half Life:The Lost Coast included in my Orange Box (what a deal!), but I don't know how it compares to the episodes or the original game.  Is it as long as the original game?  Does the story continue  the original story or have any connection with it?  Anyhow, it's gonna be a while til I run out of games, so I will consider it for a while before I make my next gaming choice.