Wow. This thread sort of exploded overnight, didn't it?
Guys, I'd
love to address your mechanical questions. I really would. I'm just not allowed to.
I'll try to answer some of the more general questions, as best I can without delving into mechanics.
Combat Length:
So far, I've mostly experienced two types of combat in this campaign.
Type 1: The players get lucky, and/or the DM misjudged something, and it's over in two rounds. (This doesn't happen often, especially as we get to know the rules better, but it still occurs on occasion. We opened one fight two weeks ago with the party rolling three or four crits in the first round alone.)
Type 2: The combat is long-running, but also takes many rounds to conclude.
What I have
not see much of (with one exception, detailed below) is the "combat takes forever in real time but only actually lasted 3 rounds of game time" scenario.
(That one exception is the fact that a few of my players are of the "casual" variety, and still haven't learned their characters' powers. So there's still some "book-flipping" slow down. But so far, that's been the exception rather than the rule.)
I can't say that the experience will work like this for everyone, or all the time, or in every group. But it's mostly been the case for us so far.
Here, let's put it this way. In 3E combat, because it took so long but often only took a few rounds, I was always bound and determined to do something
vital in every round. Yet one of the reasons I'm enjoying 4E combat is because, when I choose to, I can afford to take a round or two to really position myself for a solid strike to come--and it doesn't feel like "wasted rounds" to me.
Levels:
So far, most of my actual playtesting experience is with the heroic tier. We decided to start at 1 and just go for as long as we were enjoying the campaign.
Mechanics and prior editions:
Here's where we get into pure matter of opinion. I believe there are three possible ways to handle "secondary" rules in an RPG.
1) Don't provide them at all, and let the DM handwave everything. Basic D&D did this to some extent.
2) Try to include specific rules for everything under the sun. 3E tried to do this. Some people like the result, but others--myself included--felt that the result was a cumbersome clutter that kept getting heavier as time goes by.
3) Include a solid core, with a baseline system easily extrapolated to fit situations that aren't spelled out. This is my preferred option.
So far--and I stress
so far, I'm not making any promises--4E seems to have managed option number 3. I have a hard time thinking of any actions or skills that couldn't be pretty easily extrapolated from the existing mechanics.
In our very first 4E combat--a bar brawl, of course

--two thugs stood atop a table and menaced another PC. I decided to run across the room, slide under the table, and kick it over; since they were both standing on the far end, I figured it was a viable tactic, leverage-wise. The DM took all of 2 seconds to decide how the rules would best accommodate that, and we went on.
Noncombat Abilities:
See above, with the extrapolating. It may not satisfy
everyone, but I haven't felt their loss one iota, and I'm one of the bigger role-players of my group.
(In fact, I have a theory that including non-combat skills like "craft" and "profession" in the game actually
discourages role-playing, but it's both personal opinion and not 4E-specific, so this thread isn't the place for it.)
Previews:
I'd say that the previews you've seen are accurate
as far as they go, but even the seemingly detailed ones are incomplete and out of context.
Interesting Combat:
It has not been my experience that having monsters with fewer abilities has led to less interesting combats. The combats themselves are both more fluid and easier for the DM to run, leading him to make more interesting use of what abilities they do have. More to the point (for those asking about the pit fiend), remember that he's not meant to be a solo encounter. So even if he individually has fewer abilities to throw at the party, the DM's "team" as a whole is going to have as many, if not more, as they had in 3E.