Spell changes was irrating after playing a lot of prior editions. This came from the fact, that reading whole spell list at one stand was rather boring and when I started playing, I suddenly notice some spell doesn't work as it 'used to'.
I still hate lookin for undead turning table, same goes for Spell resistance, and dispell/counterspell checks. Wonder why I can't keep them memorized. Turning times was irrating before I made good character sheet, that solved many table-problems.
I have only one complait about AoO's. When I play, I am almost never able to get them, hey I find it hard to get opportunities for my sneak attacks. Sneaky DM-problem.
Ah, and my there is not useful useful 'table-list' of status-changes anywhere. Just that long and inpractical list, hey they made one for feats, why not this. Something I could actually use in DM:s screen.
But that one thing I still can't stand is CRs, ELs and ECLs. Ok, it was great idea, but in practise.
Even some monster CR:s are miscalculated before I even add the effect of different party combos (that different strengts and weaknesses part). Also, exp table is sadly limited.