1) Pynchon is not an author whose books lend themselves easily to adaptation (hence the lack of attempts up until now), and
2) Paul Thomas Anderson does a surprisingly good job of it with Inherent Vice.
I haven't seen the movie yet, but this does not exactly surprise me. I rank Anderson as the best American director under the age of 60 (the Coens are no longer in that category, since Joel Coen turned 60 last year).
The others who would commonly be considered as being in that conversation are: Steven Soderbergh, Quentin Tarantino, Darren Aronofsky, Richard Linklater, David O. Russell, Wes Anderson, David Fincher, Spike Lee, and Alexander Payne. There is a distinct lack of dark horse candidates beyond that group. It is hard to get serious films made today, and even harder for a serious director to sustain a career.