After two and a half years in the making, it's finally done.
With three new maps, and the whole lot redone with HDR - the third episode of this wildly popular, single-player Half-Life 2 has now been released. Requiring Valve's Half-Life 2: Episode One to play, this completes the beginning of the apocryphal, engaging MINERVA story.
Update: Read Rock, Paper Shotgun's glowing review! (But do beware the minor spoilers in their screenshots!)