I'm a big fan of optional features -- features that are, well, optional.
"Tabs or not" could be a very simple toggle in the Account settings area (not only to use, but to code). I currently take part in the development of an application that allows users to change the entire UI, with different UI's offering unique functionality. Our diverse user-base has thanked us wholeheartedly for the choice, too!!
What I've seen in this thread:
Some people are absolutely content with their inventory display.
Some people are completely annoyed by their inventory display.
With a good number of The West's more active players being paid customers, I feel it is necessary for The West to offer a compromise for both camps -- as catering to one or the other may come off as alienating.
This issue really isn't affected by the "sorting bug" that Denisero pointed out. The issue is that some people are compartmentalizers... perfectionist, easily-distracted organizers on the cusp of obsessive-compulsivity. When I want to see my weapons, I only want to see my weapons! You can never know our ADD pain!!