I'm playing it, sorta. Some modifications...
1) I've dropped the madness for men rule. Instead, all wilders have madness, to reflect the lack of training to let their brain handle the "alien" energies.
2) I've dropped Ogire, Myrdrall, Trollock, etc
3) I've added Dwarves, Elves, Halflings, and Gnomes.
4) I'm using the additional rules from the netbook that just got released
The result? I've got a great system for DnD... better than the core 3E IMHO...
I love the WoT system... the Defence rating, the casting, the "lost" feats, the low magic setting, etc. Love it, love it, love it.
As for how casters stack up? I'd say... probably about the same. In some ways more powerful than the original, in some ways less.
It's very compact, too... It all fits in one book, instead of three

Granted, that's not with a full MM for it or anything, but...
As for whats different? Well, besides the obvious, I'm finding my characters are more willing to put style before pure stats now... since it's not always suicide. I've got a fighter-type who wears only his clothes, no heavy armour, for example... and a totaly-defensive mage.