Glen,
For my part I can say it is more a case of being more familiar with it than anything else. When I had to switch over to a Windows machine (at the office) a few years ago, I tried to use Outlook but it didn't feel right. Probably has argueably great merits, but just didn't synch with me. I prefer dedicated mail software over a "swiss army knife" approach like I see with Outlook. The other nice things that I cite as reasons for staying with Eudora are the filters, and the ability to manage things here at the office as I do on my G4 at home. I prefer other software for scheduling and contact management so this way I use all of Eudora and all of the other specific programs for those other uses, rather than part of Outlook etc. As a long time Mac user I suppose there is an ingrained dislike of all that MS produces. Obviously a silly prejudice to maintain, and although I admit office is a great product, it liely will never be the case that I go for Outlook or Explorer. I prefer Netscape as next step from Mosaic. Hmmm... widespread? I too would love to know if many longtime Windows fans have moved to Eudora as a substitute for the MS products that provide similar functions.
Mike