With The Shattering having added tons of new low-level content to World of Warcraft, and the new high-level content still over a week away, me and many other players rolled alts to explore the new "new player experience". I rolled a whole bunch of low level characters for comparison, and except for previously mentioned complications with the new troll starting area, the experience was quite pleasant. The low levels are more than ever a tutorial, there are even quests now that teach you how to train new skills and abilities and use them. The structure of quests is close to perfectly streamlined, you will never run into the "what should I do next?" problem; there are now even "Hero's Call" / "Warchief's Command" boards with a big quest marker prominently displayed in all cities, which based on your level and quest history send you to the appropriate quest hub.
With all that hand-holding some players tend to forget that you of course still have total freedom to stray from that given path. Just because there is a big neon arrow pointing towards the next quest hub doesn't mean you're forced to quest. Not only can you decide to go adventuring elsewhere, but there are two major activities where you aren't led to: Dungeoneering and crafting. At level 15 you get access to the Dungeon Finder, but that news isn't all that prominently displayed. And as most dungeon quests have been moved to inside the dungeons, there is very little leading you there. And there are absolutely no quests asking you to check out crafting; you'd need to stumble upon a profession trainer by accident to get explanations about that. Not only does questing not necessarily get you into dungeons, but dungeons also might mess up your questing. At level 15 I used the Dungeon Finder to run the Deadmines, Ragefire Chasm, and Wailing Caverns once each, and ended up making 4 levels; I'd basically need to delete all my current quests and use the Warchief's Command Board to find the appropriate quest hub for me. I think I'll just continue with dungeons, the new Deadmines were a lot of fun, and I want to check out the new Shadowfang Keep.
Of course while I'm discussing the "new player experience" here I'm well aware that the vast majority of the current low-level players aren't new players at all, but bored veterans waiting for Cataclysm. That leads to another interesting observation: The "Twinkability" of different classes is different. Casters don't benefit much from stat bonuses, 4 out of 5 of their stats have no influence whatsoever on damage output, and intellect has only a mediocre effect. What they would need is spellpower, but the only enchantment that gives spellpower to items under level 35 is a rare drop from Molten Core. Even a heirloom staff at level 1 gives only 1 spellpower bonus. A fully twinked mage is better than a mage in his starting gear, but not by a huge amount. Melee classes are far more twinkable. The first big difference is that their damage at low levels depends a lot on what weapon they are wielding, and a heirloom weapon or blue weapon from the AH is significantly better than what you can get from questing. And then they profit more from stat bonuses like strength and agility. Thus a fully twinked warrior or rogue is far more powerful than an untwinked version. All that is somewhat balanced, or unbalanced depending on your point of view, by the fact that a mage starts out far more powerful than a warrior or rogue, with his first ever attack doing three times the damage of the warriors first ever attack. Once twinked, the classes are more even, but there are obvious pros and contras to design class balance at maximum twink level.
Another observation about playing a new character is at what pace he earns new abilities. In its current state, World of Warcraft's only single-role characters are damage dealers. All healers and tanks are hybrids. And while some hybrids are as good as pure dps at the level cap, they do suffer in the early levels. Not only are their spells less powerful (e.g. Smite deals less damage than Fireball), but the damage dealers get more damage spells and abilities faster. Hybrids at some levels only get spells or abilities useful for tanking or healing, which don't help at all for the soloing part. No wonder we have tank and healer shortages: A new player trying different classes for a few levels would quickly conclude that tanks and healers suck in comparison to damage dealing classes, not knowing that this balances out later.
Apart from those balancing problem, I found the new "new player experience" quite pleasurable. There are now more interesting quests and events, and even before you get your mount at level 20 there are often rides on rails (literally in Azshara) that take you to the next quest hub. For those not into questing, the Dungeon Finder makes finding a dungeon group a breeze. And Blizzard even added a bunch of mini-games, like the Plant vs. Zombie game in Hillsbrad south of Dalaran Crater. Of course, if you don't like accessibility and "theme park" MMORPGs, World of Warcraft still isn't for you. But for the average player, the low-level game is better than ever.