Hi, all... my first post on waiting4oblivion. I must say, these formus are much more civilised than the offical Bethesda ones... it's total chaos over there!
Some things that I hope they'll fix:
* Moving/equipping/using multiple item stacks in your inventory. When you clicked on a stack of items in MW, there was really no need for the dialog that asks "how many?" to be modal.
The dialog defaulted to the maximum number, and if you clicked on your own portrait to equip or use the item, the game had the good sense to ignore any answer you'd given and just use a single potion/helm/whatever. Why force you to commit to a fixed number before letting you click where you want to put it?
So, I'd love it if you still got a slider asking "how many?" when you click on a stack (defaulting to max), but you could ignore it and just click where you want to put the stuff and you'd move them all, or if you click on your portrait equip/use just one.
I also hope they allow keystrokes to influence the "how many?" dialog. I was really releaved when I discovered that the Tribunal expansion allowed me to hit Enter when moving things and accept the current default, but why not allow you to type a number on the keyboard? Fallout did this nicely, with both a slider and sensitivity to number keys and the backspace. With defaulting to max, the most common change you want is to change it to 1 anyway, so even if they just made just that key work I'd be happy.
(Of course, we don't know how the interface will work, so this suggestion may be completely inappropriate to Oblivion. I'm just going on MW, which we know)
* Built-in FPS Optimizer. I was blown away when I encountered the FPS Optimizer for MW... nominating a fixed range of frame rates that you're happy with, and dynamically modifying the graphics settings to try to achieve a framerate in that range, seems like such a natural way to do it. All games should work this way

Basically, that's what you do manually anyway - you go into the options dialog, put the graphics settings to max, drop out, check out how playable it is, go back into the options and drop them a bit, go back to the game etc. Why not have the computer do this for you?
I imagine that you'd want it to be switchable, in case someone prefers fixed graphic detail and variable framerate over fixed framerate and variable graphic quality, and ideally you'd be able to nominate the priority of graphics parameters you want to sacrifice...
(At least I can take comfort on this one, that if it's not built into the game, then a third-party Oblivion FPS Optimizer is hopefully technically possible, since it was possible for MW)
* More hot key slots. I'd like it if "0" wasn't hard-wired to unarmed, since that was a wasted hot key slot for me. However, I had an idea that would give you lots more slots - have different banks of slots depending on which modifier keys you have down (shift, alt, control).
In MW, of course, control was sneak and shift was run. But that could work well... you'd put actios and spells in the "control" set of slots that relate to your stealth activities. You'd put things you want quickly in your base set of slots. And you'd put useful but not particularly time-critical things (like casting light, mark and recall) in your "control-alt-shift" bank

Anyway, it's almost certainly too late for things to be added to the game at this stage, so I'll just have to wait and see. Pity I didn't discover Oblivion a year earlier, when the devs might have been receptive to some of these ideas... none of the changes would be too difficult to add, if you had plenty of time to debug them (which they don't any more).