My view is more towards Bryon's in that while I agree that anecdotes aren't proof and we don't have "the data", we do have our own experiences to draw from and the viewpoints of those that we encounter. In the internet era this can be substantial.
Now of course the internet and the anecdotes that we encounter doesn't prove anything beyond that some people are upset, that there is some division in the community. The question is to what degree, and for that all we can do is conjecture.
(As an aside, I would suggest we stop the argument as to what constitutes proof because it really won't go anywhere. I would also suggest that there is nothing wrong with discussing our impressions; but as soon as it devolves into "but you can't prove that" then the conversation dies. It is similar to the idea that "That's just your personal opinion, which you are stating as fact." No kidding, but let's move on, shall we? Sometimes I feel like I'm stuck in some nightmarish latter-day version of a college class from the early 90s, Postmodernism 101. ;-))
Back to the topic at hand. Again, I think it is clear that there is some division, perhaps even a fair amount. I would also suggest that, as Bryon implied, the amount of dissatisfaction with 4E is somewhat more (probably significantly so) than 3E. I don't remember as many "defectors" during that era; sure, there were some, but there was no mass exodus back to 2E, no 2E Pathfinder.
Anecdotal? Sure. But that doesn't make the discussion not worth having.
One more thing. Given that my preferred version of D&D is actually 4E, I take issue with a frequent implication that saying something is rotten in Renton means that one is a "H4TER". I like the game quite a bit, and more than 3.5 or Pathfinder or any other edition. I don't think it is perfect, in fact I think it has significant flaws, but my hope is that 5E is an attempt to fix those flaws rather than turn back the clock to sometime before 2008, or to scrap the game and start again. In other words, criticizing WotC does not make one a H4TER.