I have used, or allowed the use of, weapon specialization in D&D as long as I can remember. For a while after D&D 3e came out I even played a PC that took it, in part because it was a Fighter-Only Awesome.
That didn’t last long, even though other players in my group (whether I was playing or DMing) would take it because it increased their damage capability.
Why? Very, very simple, really: it is really, really boring. +2 damage with attacks from a specific type of weapon. Yaywn… hardly awesome, just kind of useful and limited to fighters.
AD&D specialization was no better for excitement, though it seemed even more useful.
What I want, what I really wish D&D had and what I’m working on including in Echelon, is functional differences between weapons.
Dragon Magazine #185 had an article, “The Arena Master’s Arsenal”, about the weapons of Athas. Each of the weapons presented had a normal mode of use available to the proficient, and another that was usable only when specialized. I’m not going to describe them all here, but this is the sort of thing I want to see.
That is weapon specialization I can get behind and want to take. I don’t like boring-but-useful any more. I’m ditching it in other places (no more enhancement bonuses on weapons or armor, but that armor will stop arrows — cowards weapons if there ever were any — from touching you).
Make it fantastic, even when it’s not magic. Let me do something special, then I’ll consider it specialization.