Watched it last Friday, I really enjoyed it but did have a few gripes as follows...
No mention of how Xavier was alive after X3
The whole angle with this drug that Beast had made to supress the mutant gene, while also having a handy perk of letting Xavier walk. How the hell did that happen? after other films focused on how to 'cure mutants' with these elaborate methods, but Beast has a few potions that do the trick anyway. That drug/cure has soo many potential uses in the X universe yet it was only mentioned in this film and forgotten about afterwards? that REALLY bugged me.
As many others have mentioned, how did Kitty develope powers to send people (or minds) into the past? an she could have been used a little better, as other than a bit of running through walls at the beginning she didnt do alot else.
The lack of characters from First Class present (which was my fave X-men film) and how it mentioned in a passing sentence how so many of those characters were dead. Plus they all remain dead since as the changes they made to the timeline all happen after they died.
Why exactly did they need Magneto (Fassbender) as all he did was be a dick -but thats not a bad thing, he is a bad guy and Fassbender is excellent as him- I just wish they had a reason for freeing him as he didnt seem to contribute anything to help, only hinder. Unless I missed this reason they needed to break him out.
Things I love
Blink was AMAZING, if someone told me her power was to create a few portals here and there, I would think 'big whoop' but the way she used her power was breathtaking at times! and she was my fave mutant in the movie and now want to see more of her.
Quicksilver, though he looked a bit cheesy, was a scene stealer when used. With how cool he was using his power, I can forgive the cheesy appearance.
Bishop was cool.
Was good to see them back at the end (Jean, Cyclops, Rogue) as they are an integral part of the X-men (even though I dont think it would hurt to recast all 3 of them).
Sentinals in the future were awesome and pretty darn menacing, even though the ones in the past were a bit meh.
The action sequences were awesome, particulary the future ones and (as mentioned) even more so when Blink was rocking her thing :D