The movie would be 4* or more as a Sci-Fi instead of the many Horror lists it finds itself on.
Edit: I newly watched a Spanish movie called "Timecrimes" which had a lot with this one in common. Timecrimes however was made in 2007 so this one was almost a remake of Timecrimes.
The only difference was that Timecrimes was simpler and linear with basically everything explained. Triangle plot however occurs within a loop with lesser explanation provided which was more thrilling and mysterious and elevated the experience of the 2nd viewing. In direct comparison I would say Triangle is the better movie but Timecrimes has credit for being more unique. I would recommend both movies.