The only times I've encountered a problem with grind in 4e have been when 1) The players are new and aren't familiar with how to use their powers synergistically with each other; and 2) on the 5th or 6th encounter between extended rests when everyone has used their daily powers, most of their healing surges and action points. Even then, #2 doesn't happen with every fight, usually only against encounters against Solos or against party level +2 or more challenges.
I have encountered complaints about grind at other times, mostly from players who are more accustomed to other games, like AD&D, 3e, Savage Worlds and C&C where combats tend to be just a few rounds or the rounds go much, much quicker because of the less tactical nature of combat. I don't really consider these instances of grind, however, because the issue wasn't that the monsters were sticking around for many rounds while the PCs whittled away a few HPs each round. The issue was just that the fight was lasting longer than 10 minutes real time (even though there were a lot of interesting things happening during each round). In those instances, I don't think there was anything wrong with the 4e system per se, I think 4e just wasn't a good match for those players.