Which has more sales: a single long checkout form or a multi-step one?
Interesting for me is the amount of abandonment on for the "unexpected shipping costs" issue.  I actually have this issue right now.  I'm trying to buy cheesemaking cultures and because I'm half way around the world form most of the places that sell this stuff shipping can be more expensive than the thing I'm buying.  It really bugs me that shipping calculation is usually last in the multi-page cart layouts.  I definitely abandon because I'm not willing to enter all of that detail before I know how much I'm going to be spending.