I've been hearing a lot of people saying, in effect, that 4E D&D admits what kind of game D&D has always been and tunes everything for that: butt-kicking tactical battle-mat kick-in-the-door, kill everything, and take it's stuff gamist play.  Right now I'm ignoring the later bit about what 4E does and how well it does it, and looking at the earlier bit's claims about “the kind of game D&D has always been”. I'm not convinced.
This post, right now, is sort of a placeholder. I intend to fill in my history with D&D and look at the various editions of D&D that I've got and see if they support the “the kind of game D&D has always been” remark.
As I've said elsewhere the release of 4E and the choruses of “It's not real D&D” actually got me interested me in looking back at what D&D really was, so I bought PDFs of Original D&D (from RPGNow ) and its supplements and Chainmail and printed them all out and bound them in 8.5”x5” pamphlets, in more or less the original form factor. I've read Chainmail and the three pamphlets that made up the original D&D release (X, Y, Z) completely, and have scanned the others. (Oddly enough, I've still not got beyond scanning 4E.)
The original version of D&D, along with some of its supplements, was still available in some hobby shops when I started playing RPGs, but the group I played with had was strictly AD&D, so I completely missed out playing the original, as well as its follow-ons, the various versions of Basic D&D.
Some of the retrogaming community has commented that the play experience for this for this version of D&D is very different from all versions that came after it. From my initial reading, I agree.
Blue Box/Holmes D&D
I got this boxed set for Christmas one year as a young teenager, and was fascinated. My box came with B2 — The Keep on the Borderlands. The group I ended up with, however, played AD&D. I think I ran this a couple of times for my younger brother. My original copy of the rulebook walked off many years ago, but I picked up the reproduction cheap a year or so after the anniversary.
Moldvay/Cook Basic/Expert D&D
I saw this in stores as a teenager, but never picked it up.
I bought a copy of the rulebooks (from Noble Knight) at some point, and can see why so many speak so fondly of it. It is a clear, well written presentation of the ideas from OD&D with the unevenness sanded down.
Advanced D&D, 1E
This was my real introduction to roleplaying games, and continued as the main game in the groups where I played until college, with occasional bouts of Tunnels and Trolls. We played mostly homegrown campaigns; for some reason the AD&D modules didn't work as well for us.
Red Box/Mentzer D&D
I never got a chance to play Red Box, but I got the PDFs from RPGNow.
Rules Cyclopedia D&D
I heard a lot of folks extolling the virtues of the one-book RC D&D, so I searched around a found a reasonably priced copy. Well worth the money. This is without a doubt the most complete-in-one-book version of D&D, at least until the retro-clones.
Advanced D&D, 2E
When 2E came out I'd long since moved on from D&D, and had been playing DragonQuest and GURPS for long while. I played 2E very briefly, just before 3E came out, with a guy who'd been on a 3E playtest and hated it.
Completely missed playing this at the time, but have played a few sessions during the 3.5E era with folks who played 3E.
I've played this a fair bit.