Evan Peters is like the anti-Jennifer Lawrence in this franchise. While people complain that Mystique is being forced down our throats for the sake of Lawrence screen-time, Quicksilver was a last minute addition to DOFP (and an unpopular one from MCU fans) whose role in the franchise has expanded purely because of the overwhelmingly positive reception he's experienced. That's pretty awesome.
That said, his expanded role was pretty weak, lol. The idea that a character could literally move so fast, but is figuratively stuck in place in his life is cute; but it didn't sell what is to me the most jarring age-discrepancy in the franchise. It's been 10 years guys. Why is he exactly the same as he was when we last saw him? Surely you could have at least had some fun with his 80's costuming? How old is he exactly? He came across as an incredibly juvenille 20 year old in DOFP. A man-child in his 30's just isn't a good look. Maybe this comes off as petty, or nitpicking. Characters not aging as they should does bother me a lot, so your tolerance may vary. It is particularly off-putting in Peter's case because it's such a dramatic jump and he didn't change even a little bit.
If I struggle past that, I quite like his small arc about confronting his unknowing father. It fit the theme of the film, and sat well alongside Magneto's own family woes. I don't get why he didn't reveal the truth at the end. It comes across as incredibly cowardly after the build up, especially when telling Erik might have helped talk him down and you know, SAVE THE WORLD.