A bit less than a month into the expansion, I'm actually quite happy with how they handled the transition. While you could argue that the endgame options at 55 are a bit sparse in some areas (*cough*flashpoints*cough*), I do like how they've kept the level fifty content relevant.
I've mentioned before that the gear curve from the previous level cap to Makeb and beyond is fairly smooth. The quest rewards are decent enough upgrades if your gear isn't the greatest, but wearing the previous top tier of gear I didn't have to replace anything until I got into the new hardmode flashpoints. Meanwhile the old level fifty flashpoints and operations have been retuned to drop what was previously the top tier of loot even on the easier difficulties - meaning that they actually offer a viable alternate gearing path to 55. The experience gains from this content are surprisingly good as well.
Rolling in XP in EV on my Sorcerer
Running the old hardmode flashpoints on my still-level-50 alts I find it amusing how there is suddenly value in killing extra trash and doing the often neglected bonus bosses again - after all it all adds up to experience gains, right?
I've also joined my guildies for "Imperial alt operations" two weeks in a row now, and it's been great fun. Pre-RotHC we'd pretty much stopped running EV, KP and EC on story mode months ago, but the chance to level some long neglected level fifty alts and gear them up in the process has suddenly brought them back onto the table.
It's a very social way of levelling as well, and an excellent group content training ground for alts that you don't usually play very much. Tonight I unexpectedly found myself raiding KP and EC on my Marauder, whom I hadn't really played in months and even then I was never very good at playing her to begin with. (Melee dps is about as diametrically opposed to healing as it gets in my opinion.) My performance was laughably poor in parts (it took me until about two thirds through KP to spot Vicious Throw on my bar and go "oh right, I should be using that, shouldn't I"), but since I knew the basic tactics and the content is pretty forgiving these days it wasn't a major issue. While I'll never be a star among melee dps, I felt that after those two hours or so of running operations I had already improved quite a bit compared to where I started out that evening. I was also almost level 52.
As a bonus, I finally got to see the operations story content from Imperial side, something that I never did before the expansion. Handing in the EC story quest in particular was a major aha moment, considering that I'd been wondering for months what exactly the Dread Masters' deal was and seeing how it's not explained anywhere else in the game as far as I'm aware.