If you use Swype, you can now hit enter and it will create a new line, as expected. Enjoy Swyping!
Update: Unfortunately, we have had to disable this change. It created a serious bug in the normal iOS app, causing hitting delete with one character left in an item to also trigger a “return” event, and thereby wreaking all sorts of havok (you don’t expect hitting backspace to create a new item, right?). We’ve looked into a better way of doing the fix, and are hoping to implement it soon.