I bought Half-Life Episode 1 and I played it last night, and it was a lot of fun. Valve is really good at making first-person shooters, even if they do suck ass at patching games (though I have to say the last batch of Source patches have been quite nice and Steam seems to have stopped fucking things up for the time being), and it was a lot of fun. I wrote a review
if you care to read it. Or you can just look at the pretty pictures. Your choice.