http://www.t-bag.dsl.pipex.com/halflife2.mpg (right-click and select Save-As)
Especially the second one shows off some of the nice stuff.
The graphics looks nice (considering the low quality of the movies) but what really impresses me is the environment. Objects falls naturally, you can use objects instead of just weapons to kill enemies or at least halt their movement (see the 2:ndmovie and you'll see), the enemy AI is really intelligent (Enemy chases the player - Player locks the door - Enemy tries to open the door - Door is locked so he shoots though the window instead - Player hides behind some debris - Enemy decides to break though the door).
I can't wait...