I already did tests of different fonts on different e-readers (in case I have to embed one). For books to sell it's always a legal issue, too. (One more reason to avoid embedding if possible.) Most font collections include the right to use them für print and PDF, but not for EPUB. But I do have some fonts I'm allowed to use in my ebooks – and "America Typewriter" happens to be one of them. What also works is "
Courier Prime". Both look okay (but not always perfect) on different e-readers I tried.
BTW I found out that there can also be a difference between different readers with 800x600 resolution. The old Kindles seem to use a different font rendering method than e.g. the Tolinos. On Kindle everything looks sharper, but with some fonts also less smooth (what makes using alternative fonts more difficult). The Kindle 800x600-devices work best with the built-in Caecilia font (easier to read than Bookerly on the higher resolution Kindles, if you ask me). And of courese there are different font sizes which make a difference, too. Very hard to find a font to embed that works everywhere, so embedding will never be my first choice.