Allegiance to 4E
Why will I switch? Because sight unseen I have sworn my allegiance to the new edition and embraced it in all of its NDA'd secrecy.
I pledge allegiance to 4E, and to the points of light in the darkness,
And to the demographic for which it aims,
One vision, under Mearls, rules more playable,
With roleplaying and combat for all.
Wait. I haven't seen the rules yet, so I haven't actually committed to switching, but I am very much looking forward to giving the new rules a spin when they are released. Yep, I'm buying the books. Unless the preview adventure makes me change my mind, in which case, thank you order cancellation policy.
It might startle you to find out that I'm old.
"But Zin!", you exclaim, "You're not old!".
Thanks for the pro forma protest, but I have it on expert authority that I am in fact old. My children say so.
Not only that, but various signs of age have been creeping up on me for years. I don't listen to new music anymore, only the "classic" stuff. Classic rock, Classical, Celtic; but not that *other* musical genre that starts with a 'C'. *shudder*

Music is one sign, but the creaking of my knees as I go up stairs, the doctor telling me I need reading glasses, and the white hair coming in just above my right temple (perhaps I'll have a white streak like Polgara someday), all add up to tell me that the kids are right. *sigh*
Some of the people I game with are *even older than I am!*. That makes us stodgy and resistant to change. Or so you might think. Actually all it means is that I can brag about how I started playing D&D 25 years ago, and from my vast perspective of knowledge, I clearly know more than you do.
Hahahaha, what a laugh. My apparent tally of experience doesn't mention the fact that I skipped second edition entirely, and didn't play D&D for over a decade during that time. Well, I did once, and I hated it at the time.
BECMI sets - I owned the red and blue boxes. I didn't have anyone to play with quite yet, but it sounded like it would be fun.
AD&D - I found people to play D&D with, who were eager to teach me the game, because, well, I'm a girl. Girls who played D&D were practically unheard of at the time. In fact I introduced several of my girlfriends to the game, and they played so they could meet some guys. I played because I wanted to be a spell-slinging Magic-User, brandishing my dagger against the goblin menace! Although I did end up meeting guys anyway.
D&D was all that I hoped for, and I enjoyed playing it for many years. But after a time, all magic-users started to feel the same. I played other classes until they too began to blur together in my mind. I ran dungeons, which was a nice change of pace. In college I ran my "Elves out to save the world" campaign for a year or so, because elves were just cooler than everyone else. Forget those silly multi-classing level restrictions. It's all about the elves, baby.
Later I played a faerie dragon magic user who never cast directly offensive spells; instead focusing on illusions, mind-controlling spells, and lots of silly cantrips. I unfastened the pants of the bad guys and laughed as they fell down in combat. I used illusions to terrify them, and then made yellow stripes up their backs with a cantrip (the DM let me get away with fun stuff like that - perhaps that's why I married him). Good times, but I was having to really work at it to avoid the humdrum of every ranger being like every other ranger, and every thief being... well, you get the picture.
We then picked up the Rolemaster supplement
Arms Law with an eye to using the critical hit tables for D&D to add some spice to combat. Hmm, interesting system. Let's get the other books. Once we'd dug through all the books, puzzling out the dismal organization to get the information we needed, the system looked exciting compared to old reliable D&D. We played Rolemaster as our fantasy RPG for years while our D&D books gathered dust on the shelves, and second edition came along with nothing to make me want to buy it; it was still the same-old same-old.
3E won me over because it added skill points and feats to customize your character. That, and it was easier to play than Rolemaster. That was important because we were starting a new campaign with a player who had never once played a paper and pencil RPG in her life. Trying to make her learn Rolemaster would have been a bit like dumping an English major into a differential equations class. She'd have run for the horizon so fast we'd never have seen her again. Her husband probably would have objected.
So will we play 4E? I don't know yet, but it's making me excited about possibly DM'ing again, for the first time in many years. I want to try it. We might like it, despite them taking away the skill customization that I love so much. I hope there are other means of distinguishing one magic-user... err... wizard, from the next. I truly hope so.