Levitate wasn't really feasible in Oblivion because there weren't Open Cities (unless you got the Open Cities mod). Skyrim, apparently, won't have Open Cities either -- disappointing because this makes dragon attacks scripted, but also disappointing because it makes Levitation difficult to mod in/use effectively.
EDIT: I kant spel gud.
Yeah but its just a matter of time before open cities for skyrim happens. There's like 3? Or 4 versions of it for oblivion. Anyhow I was thinking more along the lines of simply avoiding annoying mountains or other obstructions. Oblivion for example had lots of mountains to rope you into going a certain path(Or if you wanted to bypass lots of painful slogging in the planes of oblivion).
edit: I forgot to mention, it'd also be a boon to house builders. I want my giant mushroom house for my wizard. I don't want to see any stairs either. My mage doesn't believe in getting his feet dirty. That's for servants to do. (And servants don't belong on the top floor of my house, they'd probably steal the silverware.)
Perhaps a dragon mark system, it might actually fit in well with skyrim (eberron, forgotten realms setting).
Idea being you can be born with a unique mark that grants you a spell or ability. Mark of healing (guess what that does?), Mark of detection (find a creature or item likely heavy scripting needed, but it'd be cool to say find me a magic sword or point me to the nearest dragon). Mark of death (death like powers, never really explained what it could do. Personally I'd favor resurrecting my enemies staff of mannmarico style) or mark of storm (Control/endure weather, it'd be neat for vampires or were-creatures)
Being able to start with a unique ability, would give your character some additional flavor. While at the same time, I don't see any of those being to unbalancing.