A few links for you to read, if you mind.
A view of TBC raiding at lvl 80 on A Secret Agent Cat. It ends with the same point I've already talked about here several times. Challenge is lacking in Wrath. The sense of achievement we could have in earlier raids is not really here anymore, just because bosses fall one after another, and you clear content in about a month. I like the idea of 10-Man & 25-Man raids a lot, it is not a matter of difficulty, but of raiding style. A small bounded group is a stronger human experience and really requires everyone to do their best. But I really hopes that Ulduar, hard modes at least, will give us a little more challenge than Naxxramas.
I was listening to episode 1 of A View from the Top this weekend. In this podcast from VirginWrolds they interview successful raid guild leaders, and the guy said: "We need to fail if we want to better ourselves." This is so true ! Exactly why I think what we need is a difficulty that pushes us a little more to improve.
Sach Yonzon pusblished on WoW Insider today a view of patchnotes for patch 3.1 from a paladin point of view. Though the analysis is interesting, it lacks all undocumented changes. I'd advise you to read the analysis I made before, here, especially if you're holy.
Now if you're a French speaker, I'd advise you to read that post from Rominet on his blog about HL10 vs HL25 : un bilan. It tries to address the strong debate on the EU forums about the difficulty of 10-Man vs 25-Man. A lot of people think that 10-Man is too easy compared to 25-Man (most of these people are doing 10-Man content after having cleaned and geared in 25-Man, go figure). And some people are even advocating for no epic in 10-Man content (go figure more ... pseudo-elitist people).