Something I find funny about the episodic games trend is that it existed decades ago as a model for shareware, either with a game being released as seperate, self-contained episodes, or releasing the first episode as a freebie and charging for the remaining ones.
Valve's whole episodic experiment is kind of weird. But actually it has sped up their development cycle. Or at least given it more feedback. It was 6 years between Half-Life 1 and 2. The two episodes have come out over the 4 years since then. If they can get the third episode out by 2010 they'll have made Half-Life 3 in about the same amount of time it took to make 2, but with releases of sizable portions during that time.
Any way you slice it they're still doing better than Ritual, who released 1 episode of Sin and then got bought out by a casual games company.
