10 seconds of searing heat making your skin bubble would change your attitude immediately. Fire is the most painful way to go possible. In World War I -- before parachutes were invented -- biplane pilots who's planes were on fire would jump out of their craft to a certain death rather than burn in the plane.
If you were in either tower, you, too, would jump.
That may be true, but I would have to actually be burning to get to that point.
From the pictures I saw, the jumpers didn't look the least bit singed. I kinda think anyone close enough to be in the midst of the fire would have been killed from the initial impact and explosion. I could very well be wrong, but it seems to me that those who jumped did so because they were afraid of becoming burned and gave up looking for a way to survive/escape rather than jumping because they were actually burning.
Speaking from experience, I would've closed my eyes and jumped. Being on fire is not a very pleasant experience.