I think what fascinates me about this topic is not whether one likes a game or not or what one's personal preferences are--as they say, there is no accounting for taste--but what makes one actually dislike a game, or have a negative charge against it.
What is it about 4E that pisses people off so much?
It's just such a wasted opportunity.
By the end of the 3e era, it was quite clear that there was room for improvement. DM prep took far too long and was too labour intensive. The game was too complex, with cascading modifiers that meant that a change to a character's stats (for example) could mean that large parts of the character sheet needed recalculated, and stacking rules that were a good idea in principle but which were annoyingly complex to handle in practice. And monsters were both loaded down with too many intricate powers (often trivial powers) and yet only lasted about 4 rounds (so never got to use them).
WotC had also published SWSE, which was an excellent game (albeit not without its flaws), and could have served as the basis for a truly excellent new edition.
So, we could have had an awesome new edition. Instead, we got 4e.
A lot of the existing complexity had been removed. Unfortunately, it was then immediately replaced with micromanagement of effects, recharges, saving throws, and the like. They'd replaced the up-front complexity of DM prep with even more in-game complexity.
Monsters now only had a few key powers, and many more hit points. So, they'd fixed both of the problems of the previous edition. Unfortunately, while either of these fixes alone would have been ideal, the effect of the two together was to have monsters run out of new and interesting things to do after 5ish rounds, but then have them hanging around for another 20ish rounds. In other words, combat grind was the result.
And they'd also wedded the game firmly to the battle-grid. Editions pre-3e could be run without minis just fine. 3e could be run without minis without losing much. 3.5e moved closer to the battlemat, but could still work without. But 4e, with it's focus on tactical positioning and many powers that move the user or his target... I simply can't imagine playing 4e without the grid.
Now, to their credit, there have been some large improvements with 4e. DM prep is now much easier than it was. The balance issues of the previous editions have been largely cleared up. And I think the Skill Challenge concept is simply genius.
But then, that might be the most damning thing of all: 4e is just good enough to leave me really dissatisfied with 3.5e, without itself actually being an improvement.
Such a wasted opportunity.