Bill assures us that Essentials isn't a new edition, and that content is backwards compatible between both it and "normal" D&D. I think the main hangup people are getting from this is that every class since Player's Handbook was released follows the same model of power acquisition. Sure you get differing class features at level one, but after that every time you level you all go through the same motions of picking a power, picking a feat, and/or improving a couple of ability scores. This is unlike all versions of D&D in the past, where you often got new class features of nebulous utility as you leveled up (if you got anything at all).
And you know what? I'm okay with every class following the same level-up routine. In fact, I'm really happy with it, because getting a new power is a big deal. It's also more interesting that getting an often set-in-stone class feature that you cannot change, and always does the same thing. I've become very accustomed to classes getting to essentially pick their own class features instead of jotting down the one given to them. I'm not sure if this will be the case in Essentials, but from the looks of things you're going to get a mix of the two: sometimes you'll get something that let's you pick from the list, and sometimes you'll take what's given to you.
The wizard is actually a mage, and they are touted as magic school specialists. Now, magic schools are thankfully mostly dropped from 4th Edition. Some spells still have keywords that let you categorize them (Charm, Illusion, Teleport, etc), but more or less you're free to take the spells that you want and not worry that your specialist (or perhaps merely thematic) wizard is stuck with a spell that you don't particularly care for (something that's happened more than once in past editions to my wizards).
From the looks of things, the first Essentials book will only have three schools to choose from: illusion, charm, and evocation. Whichever one you choose gives you an Apprentice Mage benefit (and logically affects whatever the hell Expert Mage and Master Mage does). Nothing is mentioned as to what they do, and the only class feature really touched on is Spellbook, which I guess at higher levels will let you also start swapping out encounter spells (instead of just daily and utility). My guess is that the benefit gained will be on par with the wizard's own Implement Mastery, so I'm curious as to how they will balance later benefits against it. They'd better not say, "well since you have to take magic missile it's okay to give you something extra later."
Oh yeah, Magic Missile is a class feature (thats why it gets the caps), and every mage has to have it. In case you were wondering, it's the new version, as well. Other sample at-will spells include a reprinted arc lightning, but added in beguiling strands and hypnotism. Beguiling strands lets you deal psychic damage and push, while hypnotism lets you either have a creature make a basic attack with a +4 bonus, or slide the creature 3 squares (neither option deals damage), and since it targets "creatures", you could totally hit an ally with this and let them get away with a free attack. Just sayin'. >_>
The new class features doled-by-level gives me a distinct nostalgic feel. Like...playing older D&D editions, just with a balanced, intuitive game system. When I look at the classes from "normal" D&D and compare the two...I dunno, it feels kind of...odd? I don't think its an issue of balance but style, and perhaps the best way for me to cope with the situation is to do what Shazbot has posited: run either D&D games, or Essentials games. As always, I'm just going to wait and see instead of making unfounded accusations. Even if Essentials sucks ass, it just means ten months of not having to buy any books until they get it out of their system.