In Mists of Pandaria, there's no more talent points rewarded by quests. Instead, your talent tier rewards start at level 56 (instead of level 15 like other classes), and you get one new tier of talents each level until you're caught up at level 60.
There's really no way to get around the fact that as you start at level 55, you have to catch up on talents pretty quickly, but I still think the Mists method is a step up. You level up, you get talents. That's been the basic gist of the system even through multiple iterations, and with Mists, we see that system work for death knights too. It should hopefully make learning your first few talents a little more intuitive.
The trouble with the unholy rotation
On the downside, one thing that starting a new death knight does (and this is something that would have been highlighted even in Cataclysm, admittedly) is the somewhat uneven nature of the unholy rotation. While frost and blood still look like superior leveling trees, talents like Lichborne and Death Siphon being available to all specs could make unholy a desirable leveling spec, but for this problem of rotations.
For blood and frost, the rotation is pretty simple. You start with Plague Strike, Icy Touch, and Blood Strike, so you have the basics of your rotation in place. Death Strike comes at level 56, so blood has their basic rotation in place then, and even frost can use Death Strike until they can replace it with the nearly identical (in cost, at least) Obliterate a few levels later.
For unholy, it's not so easy. While they do get Scourge Strike at level 58, the single unholy rune doesn't fit into anything, which means they're either stuck eschewing it for Death Strike or in using Icy Touch and Blood Strike as awkward fillers until level 62, when they finally get Festering Strike. Even at level 62, though, they're not quite out of the woods. Outbreak doesn't come until level 81, and that's needed to get your diseases out without suffering from an orphaned blood rune.
Admittedly, Mists of Pandaria may actually help this a little, as you can pick up Unholy Blight at level 56 for a quick, rune-free disease application method. Still, it has a rather restrictive 1.5-minute cooldown and brings up the bloody specter of required talents.
Certainly, it is possible for a class to survive a while without some signature moves, and there's something to be said to having something to work for. I know I leveled my alt warrior through some pretty rough chances due to the hope of getting Titan's Grip when I finally hit level 69. But that same warrior had dual wielding for the vast majority of her life. Keeping fun or signature moves from a spec is arguably a valid thing. But saving a very essential cornerstone of a spec for the last few levels is another problem altogether. It turns unholy into a much more arcane and inscrutable spec, keeping leveling death knights from learning the spec properly and forcing them to only really get into learning the actual end game mechanics of it until they've leveled up to near the cap.
It's the small changes that get you
Sometimes, though, the bigger changes don't quite strike your notice as much as the smaller ones. When creating a new death knight, despite being level 55, you don't quite start out ready to ride. Instead, you have to wait until you get to the quest to get your Acherus Deathcharger (or at least until you get to your mailbox for a collector's edition or pet store purchased mount).
In Mists of Pandaria, most mounts will be shared between characters, so you won't have to wait that long. As soon as you get onto the open air platform with the gryphon master in the starting area, you'll be able to mount up with whatever mounts your other characters have collected. Of course, while you're in the starting zone, flying's still out, but most mounts still work. You'll still want to grab the Deathcharger quest for the experience, the opportunity to ride a tiny little pony all around Death's Breach and giggle at its tiny little feet moving so fast, and the unique mount for your collection, but you can ride out immediately, saving a little travel time.
On the same quest that you get your new horse, you also get the Sigil of the Dark Rider, a death knight's first relic. However, in Mists of Pandaria, anyone who's not a hunter is losing their ranged slot, including death knights. That means relics are no more. As a result, the quest item you'll be receiving is a gray item good for selling for 8 copper or keeping as a weird little memento of your time as a thrall of the Lich King.
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.