Yeah, its that being-caught-in-the-crosswind,-smacked-against-the-building-and-plummeting-to-my-death-as-the-chute-folds-up thing that bothers me... <img src="images/graemlins/wink.gif" alt="" />

Jumping out of a plane is a little different than jumping out of a building, to wit:
1) Its not very feasible to try and rappel 5000+ feet while moving laterally across the ground at 200 mph.
2) There is nothing underneath a flying plane that can interfere with a chute.
3) When you're at 5000+ feet and your primary chute fails, you have a good 30 seconds to cut away and pull your secondary. This can't happen at 300 feet - time to impact: 4.3 seconds. <img src="images/graemlins/blush.gif" alt="" />

I also agree that this is a low-probability emergency. But if I worked in a high-rise I'd at least give the matter some thought. And this site is about being prepared, isn't it?

Oh yeah, and since we agree this is a pretty low-probabilty emergency, would you rather buy $100 worth of climbing gear (that you can use for other things) or a much more expensive piece of specialized equipment?