Just a suggestion. The Define Delivery page offers Immediate Send and Send on a Date/Time. It defaults to Immediate Send and the two options are presented, visually, as two similar options. Well, I have made a LOT of errors in my time, with fat fingers, tendency to rush through lists and so on. I am NEVER going to want to send immediately, not least because your process is so smooth I normally go although the way through before checking my inbox for the tests (and getting feedback from other testers).
What proportion of campaigns get the Immediate Send?
Perhaps you could make the two options more visually distinct. I would also prefer no default.
Cockups R Us (aka John)