The latest installation of Blizzard's long standing MMO World of Warcraft brings several changes to the board, essentially reworking much of the original game and adding yet more new content and five more levels.
Deathwing has torn apart much of the original world of Azeroth, and as someone who has been playing from day one, it was delightful to see all the old haunts that have been around forever torn up or changed, like the tropics in the Barrens or the Thousand Needles filling with water. Goblins have joined the Horde and Worgen the Alliance, and both starting zones are well constructed and unique. This along with other zone changes really brings you into the game more, and certainly makes levelling less of a chore. If anything, it might be a little too easy now. 80–85 took very little time, even as a casual player, and with guild gaining levels now and giving exp bonuses eventually, levelling alts was even quicker. Unfortunately, it's bad enough that 80–85 is a fairly trivial time investment before it's back to grinding for gear to PvP raid, if that's your thing.
Gameplay wise things have shifted away from the last expansions. Talent trees have been cut back from how they were most of the way through wrath and feel less cluttered. Aside from primary stats, gear is less of an issue given you can simply reforge secondary stats like critical strike rating away into something useful. It makes gearing up less of a pain. All of the gear has been standardised a little too, in that heroic version of anything drop the same items as regular, just with better stats.
Dungeons and raids are initially harder, but as anyone who played through the end of the last expansion is likely already playing Cata, they might not be so unusual for you if you only experienced the beginning of Wrath of the Lich King or earlier BC. Things hit harder, CC is useful again (though it's no fun at all to have to keep it up to the exclusion of doing anything else, as is still sometimes the case), and healers burn through mana fast if they're not careful. Changes are still being pushed to balance out all the classes, too.
As far as endgame content goes, Rated Battlegrounds exist now for PvP, which give out points and ratings similar to Arenas and require a group to queue for. Two new battlegrounds have been added – Twin Peaks, a capture the flag 10 man, and the Battle for Gilneas, an Arathi Basin style capture points 10 man. For raiding, there are three initial raid instances; Blackwing Descent, the Bastion of Twilight, and the Throne of the Four Winds. These have a total of 12 bosses, and so far the spread reminds me a lot of Burning Crusade raid content. The fights themselves are not necessarily more difficult, but they've certainly had a lot of fun with boss mechanics so far and if you liked raiding previously, it's far more interesting now.
The new profession Archaeology, while with some decent rewards out the end, is essentially just a time sink. Everything about it is entirely random, and can make it fairly frustrating at times. Most of those I've spoken to can only manage it when they're not really playing the game – they read a book or watch TV as they fly around the world chasing down the dig sites.
As a final note, I do have a reservation about this expansion that I can't quite place my finger on. It's a far more polished and well rounded game than in the last expansion pack, and many of the changes are nothing but fun, but something has felt… Off for me, and I know I'm not the only one. It could be that with levelling taking so little time and not really being a break from the grind of rep farming or gear farming or boss farming or kill farming, and instance/PvP queues often given you a 20–30 minute wait (unless a tank or healer, as always, but even then on occasion), it feels too much like you're just sitting there waiting, doing nothing. I can't speak for everyone, but while I like the gameplay, I'm finding it hard to justify sitting around waiting rather than just playing something else.
That could well just be me suffering a little burnout though, and if you've taken a lengthy break I'd still say give it a try. The changes will keep you entertained for a while, and if you've ever wanted to level a new character it's fair less tiresome and the quests are far more fun now.