My new theory is that grind is the result of a GM not running combat well, and players not teaming up well. In the past several months of 4e I haven't felt grind, not even when this past week when we were down to at-wills, and one PC was constantly dazed by a banshrae.
I think by this point we're familiar enough with how the game runs that we never get to a situation where we're all hale and hearty, but the monsters are all bloody but not yet down. I need to ask my GM what his philosophy is for picking monsters.
Our powers give us lots of options, and the GM designs monsters with fun interactions and terrain that wants to be used, which leads to dynamic combats.
On the other hand, this past weekend I played in a 3.5 game where the GM let one player take 5 minutes on his turn, pondering all the options like he was playing grand master chess. Not grindy, just boring.
Compared to 4e, I was a lot more bored. Fighting a centaur in difficult terrain, I basically had to stay put and thwack it, because if I tried to move at all I'd be Opportunity Hoofed into unconsciousness. Then again, maybe it's just that the 4e GM designs for fun combats, whereas the 3.5 GM designs for narrative, not fun. Narratively, it makes sense that fighting a centaur in brush would be a pain in the butt. Maybe I'm just not used to things not being fun.