I think if I worked in a high rise office building today, I would seriously consider rapelling as an alternate way out. But there are a lot of alternatives to these pricey "kits."

I have actually used one of the "last resort " belts in a very short, very straightforward situation. They are bad, highly uncomfortable, and potentially quite dangerous, just as you say. I wouldn't bother with one again, because they are very heavy for everyday wear. I would use a diaper sling - cheaper, lighter, more comfortable, and much safer.

I am somewhat skeptical about a figure eight, although I have formerly used one routinely. If slack is developed in the line (very likely in going over a sharp lip like an office window) they can lock up. I would prefer either something like a Black Diamond ATC (cheaper, lighter, some what jerky) or a Petzl Stop (more expensive, very smooth, easy to adjust friction, desirable safety feature). The very best would be a rappel rack - perfect for longer distances.

One technique that anyone should learn if they acquire rapelling skills is the "body rappel." It requires no gadgets at all, only a properly anchored rope. What a hero you will be if you offer the fair maiden (or the boss) all the nice equipment, and you follow her down, depending only upon your smooth body rappel!

I would certainly practice, ideally several times, before having to use it in a stressful, pressure-packed situation (I still recall the sheer terror I felt on my first rap, forty-five years ago). Getting over the lip is usually the most difficult part and you might want to plan procedures for your specific situation. Climbers and cavers routinely rappel 150 feet and up, so this technique might offer some possibilities, but it need thought, practice, and planning - like every other aspect of survival.

Lordy, lordy, how I have rambled on. You would have thought I was discussing knives!