Players stopped coming up with interesting combat tricks, and instead just use the interesting (supposedly) combat tricks they automatically get. That has gotten boring for me.
Players complain about needing a battle map more than before.
Combat takes so much damn longer than before. Not individual rounds; they're about the same, maybe even a little faster because there are fewer fiddly numbers to track. But the combat as a whole starts with 2 or 3 rounds of cool action, and then four or five rounds of grinding down enemies' hit points until they die. This leads to me having lots of people surrender when they realize they're beaten, but in the encounters where people would fight to the death, I started just killing people at their bloodied rating, because the fights were getting tedious.
I don't want to read the books. They're ugly. Thus, I have less familiarity with the rules than I did when I was several months into 3e.
I have no idea how to make NPC stats. Like, none at all. Apparently I'm not supposed to build them like PCs, but I can't find the rules that explain it. So all my NPCs act like monsters, which gets a little odd.
Again, fights all are just PCs looking at their cards and deciding which power to use, instead of trying things that are cool on their own.
I like the core of 4e, but powers and the art just don't do it for me.