After almost three-hundred sessions both DM'ing and playing as a PC, I can confidently pick out what I like and dislike about the 4E system.
The Good - Overall I think the designers did a brave, incredible job creating an innovative rules set that reflected almost exactly how my D&D actually played at the table. Yes, the Fighter did get bored being a collection of feats with legs. Yes, the Wizard did get pissed off when she ran out of spells. And yes, my Cleric was frustrated being nothing but a heal-bot at high levels. Those things were all true and they were all fixed in 4E.
On top of that, with a selection of by-level difficulty guidelines which made improvisation an absolute breeze, and a framework for encounter building that left all the previous editions looking neanderthal in comparison, the game was a huge breath of fresh air in a 3E world with which I'd become increasingly disenchanted.