So, as well as a programmer's editor, I use ST to write fiction, documents, tech specs, etc. A text width around 70-80 characters makes that easier. ST has the ability to show a ruler in plain text, but not wrap to it.
I'd like to see ST allow one of two things;
1) A 'central column' of text, like WriteRoom does on the mac. This works well in full-screen mode;
2) the ability to wrap text at the ruler, rather than the screen edge