I hated how slow the bolts flew in Oblivion. It was damned near impossible to hit anything at any sort of distance in Morrowind and Oblivion both, they travelled so slow. You literally just sidestep and you avoid all damage. That's stupid.
Make them go at least twice that fast IMO.
Exactly right. I never played a pure mage for very long in Oblivion, but I noticed how ridiculously pathetic it was that I could shoot a ball of fire from my hand that would slowly fly past someone, and hit a pillar with a weak 'piff' sound. The magic in Skyrim is already going to be boosted with variety, but I say I would love to see actual splash damage from all magic effects in AT LEAST the school of Destruction. And I mean do this seriously, without special "spellmaking" required by anyone.
Also, of course make all spells faster and easier to implement in combat situations.
For instance, say you're spamming huge lightning bolts at an enemy mage in a Dwemer ruin filled with columns and pipes (like in the trailer), and the enemy smartly ducks behind a large piece of crumbled rock near some pillars to hide. You're both low on magicka from blasting at each other, but you happen to have learned to specialize in different schools using spells that require less magicka. You see that you can't kill your target while he's hiding and healing repeatedly, so you switch to a weak fireball on your right hand and a conjuration spell for a skeleton warrior on your left. Using up almost all of your magicka, you launch the fireball at an exposed pillar behind the mage's hiding spot. This explodes and coats everything nearby in flames, including the mage, who runs out from behind cover screaming and burning. And now, since your magicka is so low, you use the last bit to call up the angry skeleton to rush out into the middle of the room to slash the now burning mage to death while you step back and watch in a dark corner, drinking potions and healing with a smile on your face.
THAT is how a mage duel should go down in the most typical, basic, dungeon fighting fashion.