Yeah, random lagging issues are bad. I used to have an older Sony Xperia, that one lagged for about 5-10 minutes every time you connected it to a charger. The poor lad had only 3GB of RAM.
The Fairphone isn't perfect either, there have been some crashes and some UI glitches. The crashes happened less than once a month, but recently it seems like they have fixed the issue. UI glitches haven't been anything major, usually something like notification popups layering on top of each other or apps being active while in the application overview menu. They go away once you lock your screen and unlock it again.
Amphetamines and caffeine= sleepy time