iPad: There are apps that are great for writing and then there are apps that great for editing. The recently updated Phraseology does both, but it really excels when you start editing text by showing you helpful statistics.
Phraseology syncs with iCloud or Dropbox (where it also uses Dropbox versions if you want to look at older versions of a text), it has a clean and minimal interface, and you can write in Markdown or plain text.
What's notable about Phraseology is the editing features. You can pop into an arrange mode where you can move around paragraphs and sentences, or delete them altogether. You can also take a close look at your syntax, which means you can highlight nouns, verbs, adjectives and other parts of speech.
From there, you can head into Phraseology's inspect menu and see lots of data about your text, including stats about how often you use certain words, your usage of parts of speech, reading level, and plenty more. Phraseology is a solid addition to an editing workflow if you work on an iPad.
Phraseology ($1.99) [iTunes App Store]