Well, I voted 9.
I wouldn't kill, but it looks like 4E is addressing just about every real problem I've had with D&D since I started playing over 25 years ago.
Vancian magic is (mostly) gone - Check!
Starting characters are less likely to die randomly - Check!
Non-magical classes don't play backup to spellcasters - Check!
Fighter types have interesting options in combat - Check!
All classes are useful in combat - Check!
The Great Wheel is dead - Check!
DM prep looks quick, easy, and intuitive - Check!
Unified, straightforward resolution system - Check!
The thing is, I'd pretty much given up on 3e, and was playing OGL games, like Iron Heroes, but I was still stuck with Vancian magic. I hate Vancian magic. I've always hated Vancian magic. I even tried Palladium Fantasy Roleplaying because I hate Vancian magic. But all the other systems started fiddling with other things when they ditched Vancian magic. I was down to the point of writing my own magic system to merge with the Iron Heroes rules and actually get the game I wanted. It was shaping up to be a LOT of work.
Moreover, I've been trying to get my wife to be interested in playing D&D. She's interested but as I tried to explain some of the D&D "quirks" to her, I began to realize exactly how entrenched in itself the game had become. I challenge anyone here. Try explaining the Great Wheel (or Guardinals, or the Blood War, or numerous other "D&Disms") to anyone who hasn't been playing D&D for years. Watch the look in their eyes and you'll know why a lot of this stuff is getting the heave-ho. Better yet, try explaining hit points as anything other than heroic luck at avoiding serious injury and just watch the eyes roll.
In conversations with my wife, I often found myself saying "Well, in 4E, how it works is..." as I quoted from preview articles and books, like the Design & Development columns in Dragon, Races & Classes or Worlds & Monsters. Because as I gave the 3E version of "how stuff works," I was confronted by her saying "but that makes no sense!" or "gee, that seems like a lot of effort to no purpose..."
So, yeah...I'm behind 4E all the way. And, as a side benefit, the books at my game table will actually say Dungeons & Dragons on the cover again (as opposed to Iron Heroes, True Sorcery and the like...)