Many long-time Eudora users are not happy that the "new Eudora" will look and function more like Thunderbird than Eudora.
I would be one of those, and honestly, if Eudora doesn't work, I don't upgrade. 
QUOTE
I have used Eudora for ten years and there is still no e-mail client that approaches it in terms of flexibility and user-controls, particularly if a person has multiple e-mail accounts running on different servers.