I saw this a while back, it was pretty fun. I agree totally with what you said about it. I had seen Timecrimes (or Cronoscrimos, I think) like maybe a month before and it had such a similar plot mechanic that Triangle sort of felt like a more accessible rip-off to me. I don't think that it actually was a ripoff, that was just sort of the vague feeling I had while watching. And I also wondered if someone saw Triangle first and Timecrimes a month later, if they would feel the same way in reverse.