Diet Coda as good as it is, does not allow for much VoiceOver support. The app is very graphical in nature, but Panic Software did not label all of its buttons to work well with VoiceOver. This is very obvious from the beginning. Once a user sets up a site, It is impossible for a user to pick which site they want to work with, because Diet Coda does not have text labels or accessibility hints to help the user figure out which site they are selecting.
Other than that the app is lacking a few features I think would make this app Stellar. One of these include the ability to have offline site storage like Coda for Mac OS X. I also think that iCloud or Dropbox support would also go a long way to make users happy.
While Diet Coda is a great app, I cannot recommend it for very low vision or blind users, because of the lack of VoiceOver support. Otherwise, this is a very good app except for the essential need for Internet support. If your iPad does not have internet, then this app will be useless to you. This is why I feel this app needs to have offline support. Otherwise the feature set provided by Diet Coda is a great benefit to any on the go web developer.