I've only parachuted once in my life (been there done that <img src="images/graemlins/cool.gif" alt="" /> ) but what from what I've read and seen about "base jumping", even experience parachutists would have difficulty.

How far out would you have to be from the building? It's not a case of pulling the ripcord as soon as your feet clear the windowsill - if your chute inflates too close and contacts the building, then (best case) it will catch on a projection and you'll end up dangling like Neville Longbottom, or (worst case) it'll collapse and you'll drop to your death.

If I were inclined to worry about this (currently I work in a one-storey building, so I'm not), I would prefer to buy the smallest, lightest, most portable hang-glider available and learn how to fly it. H-g's are designed to leap from solid ground (parachutes aren't) and they are probably easier to control on landing. (The rectangular chutes you see at airshows, used by sport jumpers, are easier to manoeuvre but I suspect take longer to deploy; hence the "evacuchute" uses the WWII circular design - much more reliable (and hence used for sport jumpers emergency chutes)but I suspect harder to control if you find yourself being blown toward the 200' high crane on that nearby construction site.

ISTM that hang-gliding off the roof of a high-rise is at least do-able; parachuting seems almost guaranteed to fail, IMO.