Yeah, not being able to see your full inventory absolutely blows. I know a lot of whiners were saying stuff about the previous inventory, but it was much preferable to me.
Thing is, it sucks to have to click through 6 categories, on 2 or more characters, to find an item if you don't know offhand what category it might fall under (say it's a summoning doll or battlefield key or whatever). Sure, I guess eventually you'll memorize what category everything gets put in, but it's a nuisance.
Also, I like to be able to go over all my items at a glance, like if I'm encumbered, to see what I can get rid of.