No replies? A subject not comment-worthy to anyone but me, apparently.
Well, I've seen confirmation that magicka does indeed regenerate constantly.
This translation of the review from the Russian site that had the screenshots posted in another thread mentions that:
QUOTE
Magic has improved thanks to the impressive visuals and the wide fantasy of Bethesda's art team. Now it has finally become dangerous even in the hands of a novice mage, wince mana reserves are regenerated all the time - even a simple fireball can wreck havoc.
(I'm presuming the translator meant "
since mana reserves are regenerated", and that "a simple fireball can
wreak havoc"... I'm hoping they weren't saying that fireball spells wreck the physics engine

)
So, there you go. Constantly regenerating Magicka, as if you were wearing a constant-effect "restore magicka" item in Morrowind. I think that's worth raising an eyebrow over... it'll certainly improve the viability of pure-magic characters.