Another thing I've noticed in the Office community is that there's a lot of hating on Jim and Pam in general nowadays, with everyone whining about what a dick Jim is and how he's unrecognizable from S2, along with Pam. No, that's not it at all, guys. You just don't feel an inherent sympathy toward them any more because they're finally together.
To be honest, both Jim and Pam have had their jerky/bitchy moments since the beginning of the series. I could list a huge slew of reasons, but I'll just say two that stood out because I watched the episodes last night: Jim inviting everyone in the office except Michael to his BBQ was dickish, and, in "The Injury," Pam actually rolls her eyes at Dwight, to Dwight's face. I'm sorry, but that last thing is far ruder than anything else she's done (again, save that awful deleted scene from "The Deposition," which there isn't an excuse for, but it's hardly representative of the season) And again, to be honest, thank God for the fact that Jim and Pam have their nasty moments! It's obvious, since day one, that Jim and Pam are the normal ones in the office, and the reason they bonded was over that fact. If they were normal and PERFECT, it would be unrealistic. We have to have a reason to roll our eyes at them sometimes; I mean, they're not Dwight or Michael, but they're not God.
I don't think either Jim or Pam have changed to be unsympathetic. For a perfect glimpse into their personalities, I like to look at this dialogue from "The Job":
(Jan has just been fired and ran out of the corporate headquarters.)
Karen: Wow. That was some serious... hardcore... self destruction.
Jim: Yeah. Kinda feel bad for her though.
Karen: Don't! She's nuts! [they laugh]
The transcript of this scene is actually not all that accurate when it comes to the "they laugh" part of it. Karen laughs pretty whole-heartedly, but Jim just chuckles uncomfortably.
Karen wasn't a bitch, but I think this exchange was very much in-character for her. Like I just said, she wasn't a bitch, but I don't think she had much empathy. Jim and Pam do. I think Pam or Jim would have agreed with the whole "hardcore self-destruction" thing (they were both always a little afraid of Jan, I think), but I seriously doubt that if Jim had said "I feel bad for her," Pam would have immediately replied "DON'T!!!!" or vice-versa. I don't see how anyone could make the argument that this part of them has changed, though people have. Again, I haven't seen much justification for it; honestly, there is no better explanation than the fact that people severely lost sympathy for them just because the guy finally got the girl, and the girl finally got the guy.
In conclusion, no, Jim and Pam are not perfect angels. But they never have been, and it's frankly irritating to see them get victimized just because they're living a happy life together.