You know, one thing I've noticed is that the people who hate 4E the most are typically people whose favorite archaetype is mage. II think you have a good point with blaming the "balanced" nature of 4E for turning alot of people off. By giving fighter/rogue types abilities they can use in combat, it has cut off much of the wizard/cleric "specialness".
The people who like fighter/rogue/cleric types tend to enjoy it though. Oh, theres a few rogues who will grumble about the new skill system, but for the most part they're happy to have more "cool stuff to do" rather than "I try to flank the nearest enemy and poke it with my pointy thingy. Until everything is dead". Interestingly, it seems like people who really like clerics don't seem to get too upset with 4E because healing surges finally let a cleric do more stuff than, you know, cure X wounds all the time.
One gripe I do hear alot is the arbitrary distinction between encounter powers and daily powers. I think thats a genuine gripe, as its yet another abstract concept crammed into D&D. (Much like hitpoints, initiative, and the d20) But I think it is more exciting to be doing cool stuff every round rather than doing the fighter "fullround attack, yawn, fullround attack, yawn" or the "waa my wizard's out of spells so we have to stop for the day".
I just think of encounter powers being like limited, but re-usably hero points.
Although yeah it is kinda bizzare that you can only shield bash 1/combat, thats why when I DM 4E I'll probably houserule it that you can use powers multiple times up to the limit. The "five minute stopwatch to refresh encounter powers" doesn't seem more metagame-y than initiative (cmon, real combat doesn't have turns) or that all spells conviently take only 6 seconds to cast.
My personal gripe with 4E is how magical items changed. The pricing is especially ridiculous. Why would anyone bother making a Frost +4 weapon for 85k gc when you could make two +4 weapons for the same price; or ten +3 weapons.
But no edition is perfect. :: shrug :: there's alot of stuff I never liked about 2E/3E either.