OK, so, we spent the weekend playing 4e. Back-of-the-book adventure. We made 4 first-level characters...for posterity, they are:
Controller: Morgan, a human wizard of unknown gender (OotS, yo!)
Striker: Ellantry Mistymorn, female elf ranger (archer-flavored)
Defender: Unapologetic "Pol" Schadenfreude, male dragonborn fighter
Leader: Haldric Horsehung, male half-elf warlord.
Note we didn't make a rogue-zilla, and only tried one new race. Because the "striker" role was filled by the ranger, and the rogue seems to have limited purpose outside of combat, we opted against. And I may be the only player of 4e ever to actually draw character portraits on the character sheets.
About 4 hours into the game, one player said, "Maybe it's just that even-numbered D&D versions suck."
I'll spare you the play-by-play and give my general assessment.
1. Ease of play: NSM. May be an issue of familiarity, but we were looking up rules every action; in fact, sometimes as many as 5 rules to determine how they interacted. Character creation took a long time. That's mostly familiarity, but also, first-level characters are about the equivalent of third-level 3.5e characters.
2. Rulebooks: The DMG is a total waste of trees. The two pages of useful info could've been included in the PHB. The PHB didn't seem well organized to me - at one point I needed to look up movement ("If Pol's Speed is 5, how many hours will it take for him to walk 15 miles?") and the Table of Contents sent me to chapter 5. Which said, "Movement is how far you can move in a round. See Chapter 3 for movement rates."
Also, I don't think they did a good job of clarifying some terms. It wasn't until the third character that we figured out "Powers" is the generic term, but Powers are Spells for a Wizard and Exploits for a Ranger. It was confusing.
3. The Business of Gaming: The only thing that differentiates one character from another (inside a class) is the Powers. Of which the PHB gives about four. It seems clear that WotC views the PHB as sort of a freeview, and plans to issue splatbooks with more Powers. Also, I suspect classes that aren't in 4e like Druid, Barbarian, and Monk will get splatbooks.
4. Gameplay: Key point, we all had fun.
However, the most fun parts were things the DM created. The adventure as written is just five fights. The DM added some interpersonal stuff to try out skill challenges and skill checks, and that was the only time we could really roleplay. (I like the skill challenge concept, btw, and will be incorporating it into other rulesets).
4e was quite good as a tactical fighting game. We were punished if we used poor tactics and rewarded for using smart ones. Individual character builds are balanced to a fare-thee-well (which I hate), so what's important is your party build. The only "role" in 4e's claim to be a role-playing game is that of Leader, Striker, Defender, or Controller. I.e., what you do in combat. The main result of the party-build concept seems to be that you either all survive or it's a TPK. In essence, the party is a corporate entity, and it lives or dies.
(In some ways I'm okay with this, as it forces player cooperation...but it also forces the DM to be the foe of the players, which I've always thought was stupid.)
The move action/standard action stuff is a little different, but easy to grok. At least at early levels, it seems that they have done away with your reliance on magic items to be strong, instead making your Powers the key point.
Final word: It's a superhero tactical fighting game (Champions) in a high fantasy wrapper. It's fun, but I don't see where it adds any value over playing Descent or World of Warcraft.