To correct some of the reviewers here ...
Primer was shot in 16mm (not a digicam).
Shane Carruth used filters and a variety of other traditional photography/videography techniques to give it an intentional, overexposed look. Reminded me a bit of other recent noir thrillers like Pi and Memento. Loved it. Perfect. Had it been a digicam, it would have been a completely different movie...but the fact that you didn't notice is a compliment to the director.
If you didn't catch the entire plot the first time through (especially the ending), it's definitely worth a second watch. The two main characters were confused & twisted in the end, and the filmmaker wanted to take the audience on the same journey. Brilliant decision.
I remember critics watching films like Total Recall (original) & Vanilla Sky a second time...why does Primer get singled out for more criticism simply because it's independent?
The budget was $7,000. This entertained me more than most movies with $70 million budget. And it raises so many ethical and scientific issues, it makes you think. View this movie like a complex novel - if you're not in the mood to really engage, go watch Battleship or Transformers.
Shane Carruth was the writer, the director, the star, the editor, & wrote and performed the music score. Amazing.
Primer won the Grand Jury prize at Sundance. The acting was impeccable - I think the filming style and the 16mm helped cover up any shortcomings of the entirely amateur cast, because I didn't notice any weak scenes at all.
For me, this movie gets the highest possible score, and I can't wait to see his next film Upstream Color.