No spoilers, not really.
Edited to add: however, this is one of the few comic book movies I’ve seen that is written just like a comic book (i.e., you’re expected to know what’s going on or catch up). This references X-men, X-men 2, X-men 3, X-men Origins: Wolverine, and X-men: First Class. If you have not seen any or all of them, nor are familiar with the comics, you will be confused. Hell, for my viewing, I had only seen four of the five movies above and knew the general plot of “First Class.” There was one scene in which I missed most of the emotional impact because I did not recognize characters from “First Class.” For all that, I did enjoy it, but there might be some people who don’t appreciate being thrown head-long into a plot with little to no context (there just isn’t time).
1) The wibbly-wobbly, timey-wimey ball isn’t just for the Doctor.
2) So Shadowcat apparently has the power of plot convenience.
3) Wolverine was right about Magneto.
4) The amount of screen time in a movie apparently has no bearing on the actor’s place in the end credits.
5) Xavier is really whiny. Good thing he turns into Patrick Stewart.
6) So, one f-bomb is allowed in a PG-13 movie.
7) Storm should have had more screen time. Why? Because Storm is awesome.
8) Movie studios usually don’t share properties even when they bought the rights from the same company; good thing Disney and Fox had to share (Spider-man is out of luck, though).
9) I can overlook severe plotholes if I enjoy the rest of the movie enough.
10) There is a right way to reboot a franchise. Of course, it helps that time travel is actually a viable mechanism to do so.
And again, the litmus test for fans vs non-fans is the sequel teaser after all the credits:
Me (and other fans) – GAAAAHHHH!!!
Non-fans – Huh?
Also, Guardians of the Galaxy looks like it will be a lot of fun.