they are... excellent. you can get the full 600mb one from fileplanet, but if you want smaller chunks, do a internet search for "half-life 2 e3 video" and you'll get results. i especially liked video #2 - here's a link where you can download it...
http://pldod.gamevision.g2h.de/patches.php?load_id=45&filename=e32k3-halflife2_pce32003_2dn_qt.zip
the AI is totally realistic and every object in the game is responsive. (ie, you can shoot out wooden floorboards and it breaks like wood. you can block doors with furniature, etc.)
...and if you're interested in future modding, i've already gotten something/people arranged. PM me.