I still use it for ‘real’ (own domain) email, while using a popular web service for web logins and other junk attractants. I have an OS X 10.6 machine to run it along with some other things that I don't want to ‘upgrade’ (e.g. non-subscription Adobe CS). The main missing feature is UTF-8, but as an English speaker it hasn't been a problem in practice.
Eudora was recently donated to the Computer History Museum¹, so there's some faint hope of a revival, although it would more likely be the inferior Windows version.
¹ http://www.computerhistory.org/atchm/the-eudora-email-client...