There's too many Argonians in this thread, lol.
I was so excited about the Horses in Oblivion, I know they were in previous Elder Scrolls games, and in TES 1 and 2 you can fight from atop the horse, but then when I found out that you couldn't fight on the ones in Oblivion it just ticked me off kinda'. I forgive them, I know the animators for TES aren't the greatest, and if you don't feel you can do something well, then don't do it at all.
When Skyrim was still in the making, I gathered up my hopes that they'd add mounted combat...
On one hand it would shift the balance of the game. Everyone would be riding around on horseback and when fighting someone that wasn't mounted they'd be in serious trouble. So on one hand I would love to see that happen, on the other I'm trying to work out in my head how it would be done without shifting the balance too much.
As far as different mounts, I don't really care. Maybe riding a bear into battle would be cool, but it seems like it might take the entire game off down a strange path. For the devs to do it they'd have quite an extreme task to undertake, and I'm sure at least one member on the Bethsoft team may have thought about it, but it probably was shot down by that same person when he realized what it would take. I'd think they'd try for mounted combat first.