I don't know if other people feel the same way, but when I first started Dredmor it seemed super awkward to me that you do Shift + # instead of just pressing the # key. In almost every other RPG type game with a hotbar, you just press the number. So: Instead of Shift + #, for belt items, just # Instead of # for spells and skills, use F# keys.
Or maybe the ability to completely map each slot to a specific key. Of course the default 1- 9/shift 1-9 would be used.
I would've supported that idea, if not for a little thing. Most of the time I'm using a laptop, and actually using function keys requires me to hold a button ("function switch") that is further from those keys than Shift is from numbers. So I'd have nothing against switching it so that skills would be selected with Shift + #, or if we could choose which setting do we want to use, but in the proposed form it's nothing I'd wish to get.
A complete hotkey assignment interface would be the best solution. Then you could assign whatever keys you want to any of the game's functions.