I played through Costume Quest in just two sittings. When I finished the game I was satiated, but, like Chinese food, I was hungry for more pretty soon after I finished, which led me to buy the Add-On quickly after my completion of the main story. Downloadable titles have an opportunity to become what companies and consumers have wanted games to become since the turn of the century (Wow! That sounds weird). Half-Life failed at making its story episodic, Penny Arcade Adventures also stopped 2/3 of the way through and has just started to finish the story on their website, and there are many more instances where episodic gaming has failed.
Recently though we have had more instances of games actually succeeding with the episodic model. Telltale, of course, has made an empire out of being episodic, and Hothead, the studio behind PAA and the new Ron Gilbert project, DeathSpank, have become more mainstream than niche. Double Fine has a unique opportunity to become another studio that puts out great episodic content. I wouldn't mind having a new Costume Quest title every Halloween. I think that smaller titles such as these have great potential to help comedic games find a better market outside of boxed retail.
The sign of a great game is a game that leaves you wanting it after it has finished. Like with me, moments after I finished Costume Quest I went back to the store to buy the Add-On. The same was true for DeathSpank, even before I finished DeathSpank I bought Thongs of Virtue as soon as it came out. These smaller titles are a good value and I think that with the number of great games being released to stores there is less time to play things that might have been niche titles in the past. Comedy titles especially are in trouble of falling through the cracks, and we needn't look any farther than Double Fine's own Brütal Legend which sold dismally.
Smaller titles gives us the same feeling that a larger title does, but the company doesn't have to invest as much time and money into its production, which, in the end, is going to be better for the company and the consumer. We could all use more time.