CJ,
For me personally it comes down to this. I'm using Firefox and Opera because I'm tired of having sites try to Hooperize MSIE. And if I look at my own sites and they dont look right, I cant fucking stand it, so I fix it. I'm not Gonzo, if there's a big red x in the middle of my page or a table is out of alignment, it drives me batshit.
What I'm seeing so far is people who hand code (myself included) usually get it right. Pages produced by designers who rely on software generated code are looking a little funny.
And you're right the percentages are small, but I sense a momentum shift....I'd rather have pages I build today be "right" than perhaps have to recode 6 months worth of work if AOL were to suddenly switch to Mozilla in Q4 and raise that percentage.