I was thinking "Aracna Evolved!", too! Pixies and witches!
The pixie looks mighty interesting. Not for all games, but for those who with more whimsy and a heavier fairy tale bent.
Well, flavor-wise, sure, but flavor-wise, an orc can have whimsy and a fairy-tale bent. It's good to see it, though I wish they didn't pretend like gnomes didn't already exist in the fluff, there, maybe differentiated them a little bit more (though I suppose they fill pretty similar places).
Mechanics-wise, it seems a little...kludgy. Nothing like taking some nine year old girl who is all pumped about playing a pixie knight and slamming her face-first into the brick wall that is D&D size rules, artificial altitude limits, opportunity attack weirdness, and "it's balanced and that's all the justification we need!" reasoning. Not insurmountable -- a fun concept can power through mechanics weirdness like a hot knife through butter -- but it would be
really nice if I could play a pixie without having to interface with all those little brute-force fiddly bits.
Witch seems promising. You could easily use the Witch to mimic the Al-Qadim sha'ir (using your familiar/genie to change your daily spells). For that alone, I give it a thumb up!
I am surprised it's not a warlock. Given how closely warlock and witch are bound up in fantasy and terminology, it would seem the clear front-runner choice! It even references familiars as sort of pact-related!
Now everything arcane is a pact? Swordmages are just wizards with a "sword pact!" Mages and Wizards are just wizards with a "Book Pact"!
Depending on the kind of "Witch" archetype you're going for, some sort of arcane-and-primal Warlock seems just friggin' peachy. Another arcane controller might work fine, too, but I'm a little worried that as another wizard-spell-user, it won't have much to distinguish it from the other arcane controllers out there. Witch vs. Wizard|Druid(or even Shaman) Hybrid who picks Enchantment spells...difference?
Not that WotC seems to care too much about reinventing the wheel (how many different ways can you be a vampire?)...which I'm kind of in favor of! As long as the witch can do something unique and interesting, she probably earns her place in the class pantheon, at least as much as red-headed stepchildren like the Runepriest and the Seeker do. So far she doesn't look that unique or interesting.