One could argue that the ad hominem attacks are largely toward those that find RPing in 4e hard. It's clearly our fault. We're doing it wrong or haven't given it a real shot. I'm perfectly willing to admit that I'm not a great RPer. I'm good in good RPing groups, but I can't pull a group along with me.
Unfortunately, ad hominem attacks are not in the employ of just one side or the other. They abound. 'You’re doing it wrong' is just as much of an (and a more blatant) ad hominem attack (and unhelpful to boot).
So those of us that really like 4e (and I do) but find it hard to get a good RPing session in are somehow not giving it a fair shot? I think that just because others have different experiences than you doesn't mean that we aren't doing our best with it.
No, I am not saying that at all. If I sounded dismissive, or that I have contempt for those who dislike 4e, then that was not my intent. What I’m trying to express is a) it’s something we all do (it’s a human being thing (and some cool neuroscience discoveries recently showing how it works at a brain-scan level)) and b) for some who try/tried 4e their confirmation bias led their initial game to be an unpleasant experience.
Mainly I put that out there to respond to the OP’s experience with the player who had a player express the ‘you can’t RP in 4e’ sentiment before they even began playing the game. I don’t know if that player ever tried 4e before – maybe they had and their experience was that RP was hindered – but if they hadn’t and went in with that notion without managing it then it is more likely that they would not have RPed and would end the session with that sentiment.
People can give 4e a fair shot and come away disliking it. People can give 4e a try unsure if they’ll like it, or even with misgivings, and realize they simply have uncertainty, and come away having given 4e a fair shot and liking it (or disliking it, as the case may be). In my own gaming group, when I ran my 4e test games, I had players who came who ranged a spectrum from ambivalent to wary to curious, and one player whom I didn’t expect to show up given his ranting about how 4e was an anathema to everything D&D. By the end, some of the curious players were not keen on 4e, some were, while some of the wary players ended up liking 4e. The one who thought 4e was an abomination played in a fashion that confirmed everything he said was horrible, and left with his opinion intact.
Returning to where we are in this thread, I am totally down for someone (as you are generously doing here) saying something akin to “our campaign seems to have less RP in 4e than it did in previous editions” and open for musings why and/or ideas to take back to the gaming table, or looking for what hindrances may have cropped up that when smoothed over the RP floods back naturally. I have had a different experience than some others with 4e as it has enhanced RP greatly compared to 3e; that we have had different experiences is fascinating to me, I have no judgment about the other group/person (or myself, for that matter), and love to explore it. Heck, everyone’s campaign likely has room for improvement in certain areas, so sharing our experiences and thoughts is a great way to grow.
As I think about it, the biggest problem is that it's hard to run a "gritty" game in 4e. The PCs are so powerful and special. Try to adapt an old 1e or 2e module to 4e. It's really hard.
Indeed, 4e is not set up to be as gritty (as most would use the term, I would surmise) with regard to damage without some modifications (of which I wrote up some). Whether that’s a 'problem' or not depends on the style of campaign… and clearly if you want to run a game with that grittiness then it is something that'll need to be addressed.
Amusingly, I am running a 1e module in 4e right now (H3 to be exact). It’s epic level in scope, so it fits well within 4e’s epic reaches....
Again, I really like 4e. I found 3e to be overly complex past about 7th level. I found 2e to be largely okay and I found 1e to be fun but not a consistent experience (the rules were just too vague). I just think that 4e has it's own problems (as does every game) and we should try to identify what those problems are (though people will of course have different issues) and see if we can't find some good workarounds.
Bingo. I’m fully in step with you. There are niggles we can take with every game (including plenty of bits of 4e that I’m not fully keen on), and we call can create and show off our modifications, thoughts, solutions, etc. And all have fun doing so!
I've read quite a bit of fair and reasoned criticism, where people have expressed what they don’t like.
I've also read quite a few responses where a person assumes that, if you criticize aspect X of Z, it means that you dislike all of Z, and all who play Z. That simply doesn't make sense.
No disagreement from me here at all. Just as I would hope that by me saying there are those who may (mostly inadvertently, as these things work) not have given 4e an honest go one wouldn’t suppose that I was saying EVERYONE who dislikes 4e didn’t give it a fair go.

Or that I like 4e means I disliked 3e, or the fact that I generally like 4e means that I have no suggestions or thoughts on what to add or improve (if I didn’t I wouldn’t be selling product on RPGnow

), or anything of the such....
If Mr Mearls wants to contact me to help make 5e, I've got ideas for him... maybe we would end up working together RC in doing so (and others!).
peace,
Kannik