Re: Inventory fatigue
The thing is the original Deus Ex made it an interesting problem. It had a fantastic interface optimised for mouse input in which you could drag and drop and arrange your weapons and inventory items in a grid, and the choices really came down to the guns and ammo you could carry that had a huge role on how you played the game.
In Borderlands you had one of the worst possible interfaces ever designed, optimised for an XBox controller, with no attempt made to facilitate mouse navigation (often you were not allowed to click on buttons, you had to press a certain key, and the mouse wheel would not scroll anything). You had to use the cursor keys, press E, X, Enter, Page Up and other awkward keys to accomplish things. Scrolling (with the keyboard) was nearly always required because the menus had to be big enough to be viewed on low resolution TV screens.
Furthermore the problem of inventory management was not an interesting problem in Borderlands. You picked up a new weapon every few enemies and this required comparison with all the weapons currently in your inventory if you wanted to make an informed decision of which weapon to drop to make room for it. You couldn't view all the weapons at a glance, it was just a list that you had to scroll with cursor keys and frustratingly navigate with the keyboard. It was a chore. It fatigued you, particularly mid to end game, and made you not want to play.
It was even worse after a break because you would forget which of the weapons in your inventory (out of potentially millions) were the ones you wanted to save, so when you pick up new ones (or if there were some you had intended to sell when you got to a shop) you would need to spend a lot of time looking through the inventory to determine which shouldn't be sold.
I've not played Borderlands 2 yet but I can only hope that:
a) better interface with more of an attempt to optimise for PCs with mouses
b) inventory fatigue is less of an issue