The great folks over at The AVClub have a great article
about the future of the American television seasons. Noel Murray and Scott Tobias have a fantastic in-depth discussion about 1hr dramas , 1/2 hour comedies, 13-episode seasons, 24-episode seasons, and more.
Personally, I think that quality network dramas (i.e. "Lost") would benefit significantly from switching to a 13-episode season. Yes, this means less money for the studio, but creatively it would mean significantly less 'filler' episodes, you know, episodes that do not forward the main mythology of the series. More meat, less fluff.
In its waining years, "The X-Files" had far too many 'filler' episodes. I mean, those last three years were all 'filler,' weren't they?