One of the many things I like about writing in the digital age: you can compose your text in any typeface you like, from Courier to Comic Sans — you can even write in Wingdings, if a wayward spirit so moves you — and then convert it for submission into whatever font it is that your publisher wants even if what your publisher wants is so butt-ugly you couldn’t write an original sentence in it to save your life.
I like to compose in single-spaced Courier New, then double-space it for editing and revisions. Sometimes I’ll switch to Century or Times New Roman, just to change the physical layout of the words on the page, and their relationship to each other — it’s an easy way to get a fresh look at the text if it’s starting to get stale. Double-spaced 12-point Courier New is good for doing printouts for readings, because you can get a good estimate of time that way: One page with standard margins is roughly 250 words is roughly one minute if you’re reading it aloud. But again, you can always get the estimate, then switch to some font you like better. (Orator, as its name implies, is a good clear font for making reading printouts, though it does take up more paper than Courier or Times New Roman.)
Everybody has their typographical preferences, and in this age of electronic writing, we get to indulge them. And it is good.