Mr. WHO most likely hasn't played Half-life 1...which is a pity...cause it's a kick arse game!
As for HL2...if you've seen any of the older footage...the source engine could do CRAPLOADS more than it can now...for instance...'blow holes in wooden objects'...like...actually shoots bits out the wood, so it can snap under it's weight and stuff like that, they also took out the 'gun cleaning kit' which was mentioned a few times (clean your gun after every fire fight to make sure your gun doesn't jam in the next one)
AS for the story...uh...seems pretty straight forward to me...Freeman is a hitman...killing whoever he's told to kill...'You knew your contract was up to the highest bidder, didn't you?' Someguy says near the end of the game...
And yes WMCoolmon that thing rules! It feels like you're a god or something..."Out of my way puny mortal" *BZURT*
Fun fun