A major issue with inventory for me is managing items across all of my companions. I like recruiting every available companion, even ones I may never/rarely use in my active party. Then, I like equipping all of those companions optimally with my available equipment rather than saving my "best" equipment for just my active party. This is a major roleplaying element for me. As such, having an inventory UI screen where I can access the equipment of all of my companions simultaneously is critical to make it easy to move items around across all those companions. NwN2 is a good example of a game that did this right. By contrast, in the DA games and PoE, you have to swap companions in and out of your active party to move items around, which is such a huge pain.