I've only seen a few episodes (and half a film) of HighlanderHighlander, and I never really understood the Quickening:
The Quickening is the receiving of all the power and knowledge another immortalImmortal has obtained throughout his/her life.
If that were true, there would be enormous differences in power between two immortalsImmortals (an old immortalImmortal being a thousand time more powerful than a new one for instance).
But it seems to me that all of them are very close in power. How is that possible?