Look, I love Illustrator [and CS6 is not only blindingly fast over CS5 - but packed with sweet new features] - but I'm glad I was a cynic and did something that I've been doing since CS4 [at least].
Namely creating a folder [of folders] of all my Brushes / Swatches / Scripts / Styles / Templates / Actions / Workspaces etc. [I would list custom Stroke Widths over here. but I don't know where that info's kept] before installing a new edition - as the new versions [still] don't ask whether you want to migrate these from your current instalement [so had I not have done my aforementioned, I'd have lost all my custom support I've collected and made over the years].
This would be a nice UI / Consumer amendation for CS7 and beyond - thanks!
Europe, Middle East and Africa