The way you managed your inventory in Oblivion had some serious issues, however to my dismay things are even worse in Skyrim. In Oblivion you had two advantages that are vanished in Skyrim
The first one was that you selected a mellee attack and a spell and now you could attack with both of them. In Skyrim everytime you want to attack with spell you must go to your inventory and search for it.
The second one was that in oblivion you selected 9 favorite attacks and you could instantly change to them simply by pressing 1-9. In Skyrim you still must press Q and find the specific attack you want.Scrolling down is always more annoying compared to typing 3 or 4 till you find your spell
This means that i end up using far less type of attacks that i would like to use. Take for example dragon shouts. You have around 20 of them and some of them are awesome. Isnt slow time awesome? Isnt the Storm Calling great? Well guess what. I end up picking only unreleting force and Fire and Frost Breath. 95% of my shouts are these 3 which is sad since i have so many good shouts to use. The same can be said for spells
Wouldnt be better if you pressed a button to show your spells without going to the main menu and searching them?