Having run the risk of wearing out my enthusiasm for demonic invasions (though they are so much better for testing a spec than target dummies,) I decided to try leveling up a new character from level 1. I picked a Worgen Rogue - Worgen because Gilneas is my favorite starting zone and Rogue so I could be an Outlaw Pirate (which somehow fits Worgen really well.)
There's a bug preventing me from continuing, but I did manage to get to level 11, so let's see what we've got:
First off, all classes now start with a specialization picked out. Because there's way, way less overlap between abilities among the various specs, it would have been harder to have those first nine levels as a generic member of your class.
Rogues begin as Assassination, which retains a lot of the old Rogue themes. I also saw a Warlock questing around as Affliction, which again, is probably the closest to its classic incarnation of any of the Warlock specs.
They seem to have taken some care to make sure you get some core rotational abilities early. Rogues begin with Mutilate, and quickly get Deadly Poison at level 2 and then Envenom at level 3, which allows for you to do the most rudimentary version of the Assassination spec pretty early on.
You get Stealth and Evasion as well in these earliest levels, though Stealth is a little funny, as you don't actually have any stealth-based abilities for quite a while.
I also noticed they got rid of the Cataclysm-era "use your second ability, and here's how to talk to Class Trainers" quest, now that class trainers are almost entirely purposeless now. Maybe scratch the almost.
It may be simply that the PTR didn't copy over my heirlooms (though I did get the Chauffeured Mekgineer's Chopper,) but it seems as if enemies last a bit longer. I wouldn't be surprised if they buffed the health on low level mobs to counter the way that players deal way more damage than they used to.
Once you hit level 10, you gain the ability to change specs. In case you hadn't heard, players can now change specializations any time they could previously have chosen between their dual-specs, for no cost.
The alternate specs - Subtlety and Outlaw - both start with a comparable number of abilities to the ones that you had in Assassination. Outlaw has Saber Slash, Run Through, Stealth, and Riposte, and then gets Pistol Shot at level 11.
I suspect that specs with a vastly different weapon type might have an awkward period - a Hunter who chooses to go Survival, for instance, might still have to stick with the starting spec (I'm assuming Marksmanship, though I don't know that for a fact) until he or she can get a melee weapon, but they'll also have to know to switch specs before turning in quests to make sure that they get the right one. Granted, after switching to Outlaw I did find a quest that rewarded both a dagger and an axe, so perhaps you'll simply be given all the options your class can use.
Obviously, having played for just under ten years, I can't really put myself in the shoes of a totally new player, but the scratching of surface I've done here suggests that there is at least a decent introduction to basic class concepts early on here.
I didn't see what all the levels one gained new abilities were, but I think erring on the side of earlier is a good idea. Let the later levels bring in weird utility spells and the like, but let the class play like it's supposed to pretty early on.