This is a great thread - I've bookmarked so many suggestions, thanks!
I'm currently using a Swiss Army backpack, and really wish I could find a nice, stylish backpack or laptop bag that could hold my laptop, purse, water bottle, book, and laptop accessories (to stick to the 2-bag carryon limit). And if it was a bag versus a backpack, I don't like having an open top that could spill items. It seems like there are nice laptop bags and totes, but many are good for day-to-day commuting, but not necessarily travelling for a week.
Oh, and it needs to be lightweight. The color pink would be good, also.

I think I'm getting carried away....