Primer, much buzzed at Sundance, is probably the best time travel movie ever made. It's still not a great movie, but it's nicely put together.
It looks fine. And since it's about the high tech stuff some young engineers throw together in the back of their garage, it looks fine without needing a ton of budget. Well acted, and written with respect for the audience's intelligence. I'm not sure that the editing is as taut as it could be, but some shots that seemed ornamental to me might be filling in clues and details I missed.
The underlying problem is simply that the modern time-travel paradox story is inherently cerebral. It's an insider game that's been played amongst fans for decades. Trying to do it in film means that you have to keep track of the score while it's moving in real time: it's an interesting exercise, but it's really hard to keep track of the temporal mathematics while caring about the characters and keeping an eye out for unexpected tricky business.