These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Music of Awesome: The score overall is great, in particular the music in the opening scene, which has a very eerie, dreamlike quality to it.
Disproportionate Retribution: Some have theorized that the time loop is a divine punishment to Jess for abusing her son. However, she shows genuine remorse for doing it, and it's hard for the audience not to forgive her pretty quickly.
Fake American: All of the main actors (and a few of the ones playing minor parts) are Australian. Also the ship itself; according to the life preservers, it is registered in Miami, but it is clearly modeled after the British pre-war steamer RMS Queen Elizabeth, and even betrays its origins by using the Commonwealth spelling of "Armoury" instead of the American "Armory".
Fridge Logic: Many a commentator on IMDB forums (http://www.imdb.com/title/tt1187064/board/?p=2) has valiantly tried to explain the reason why the time loop resets some things but disregards others (the dead Sallys, Jess' lockets, and the dead seagull among others) only to fall flat on their theories.
The scene where Sally staggers into a section of the boat filled with dozens (maybe even hundreds) of dead versions of herself.
A chilling moment during the ending. Jess is driving away with her son and it seems that all is going to be well, even though something is a little ... off. Then, suddenly, a seagull flies into the windscreen, dying instantly. A shaken Jess leaves the car and goes to dispose of the body on the beach... Cue the pile of seagull corpses, as Jess realises this isn't the first time she's done this.
Too Dumb to Live: Phelous constantly bemoans the lack of common sense that plagues the cast throughout the movie. Like why the other Jess keeps fulfilling the time loop by keeping herself hidden and spying on herself rather than just reveal herself to the pre-time cast and stop the entire mess from happening, or why Greg assumes the people in the boat are hiding from them for fun rather than just letting them know of their presence.
To be fair to Greg, he is very rational-minded, and was just trying to find a somewhat sane explanation for why the ship appears to be deserted.
As for Jess, the first time it loops knowledge of what is going on doesn't instantly and magically pop into her head and thus she can not yet have decided to stop the loop. When she do figure it out(at which point she does confront them and try) it is already too late. The second time it loops she actually intends to kill them in order to use their boat to get away.
Phelous also points out how Jess seems to just insanely conclude the loop is murder based, despite the same amount of time occuring in each iteration and the fact that there are multiple Jess' in each loop, so why does she think killing herself will reset the loop?
It is not made clear whether or not the same amount of time occurs between each loop and the loops we and Jess are shown always and instantly occur when the only ones alive and on the boat are two of Jess, plus something must have happened in some earlier instance of the loop to make one version of Jess come to this conclusion to begin with. Also it is never stated that murder is not what causes the loop, so her being wrong is just an Epileptic Tree on Phelous' part.
What do you do when you see a message saying 'Go to the theatre' written on a mirror in blood?