Federico Vitticci's in-depth review of Editorial for iPad is as profound as the application itself so I'm not going to say anything more than go buy the application if you need to write anything on the iPad. It's really good.
Update: Federico has created an e-book with an expanded write up, 15 demo videos and 50 downloadable workflows for Editorial for iPad. It's on sale at 50% of the $5.99 full price for a limited time. Go grab a copy and support a great writer.