Until recently a buddy rode a '10 (or 11?) I rode an '04 for a season. Biggest difference was the trail worthiness of the new v. the old. They're still pigs, but you can actually get away with a fair bit of climbing here and there. He did "push" the rear, as well as pop in a volume reducer, which dramatically improved the way the bike used its travel, which has always been the gripe for those things. He had a new'ish Bos up front, which was ridiculous. Some of the lesser known suspension companies these days are putting out products that should really put the big boys to shame...but they're all really pricey.
Minons front and rear.
I think the new ones have gone a bit more slalom/slopestyle, no?
SLX these days is pretty nice, maybe less so in '11. You're right, though, the parts spec on the Stumpy is better. But 5 years of wear and tear, and a few generations of tech improvement might even that score.
Little differences in geo make for huge differences in ride, and as mentioned, the pedaling platforms will feel different, shock aside. If you're still xc inclined, and want to try 29ers, I say go for it.