Re:Misconception (Score 2, Insightful)

Agile development is not about speed but about change

That's true. But being agile means that sometimes, you can dodge the speed-bumps.

the practices proposed in [...] XP might lead to a faster development but will never ever guarantee on time developement

It depends what you mean by "on-time". XP can certainly guarantee that something will be delivered on the appointed release-date, and that it will contain the most important functionality. You relax the scope in order to hit the target. In some non-XP projects I've been involved with, we've been unable to alter scope, and therefore had to relax quality to hit the target. And that's never a good feeling.