I'm continually being delighted with how slick this system is.
Yesterday I migrated my e-mail from Eudora X to Mail.app. I got tired of waiting for them to come out of beta. Other than that, I really like their product and would recommend it over OE.
I've never used Mail in any big way before and I'm very impressed. The one minor nit is that Rules aren't as powerful as in Eudora but Mail makes up for it in other ways. The 'Bounce Message' button alone is going to be *sweet*!
Another neat tool: Watson. It's essentially a front-end for Web services such as moviefone.com and Yahoo!, which allows you to query and grab the essential data without futzing with all that excess HTML and it will even auto-update in the case of stock quotes and similar data. Kind of hard to describe, but seriously cool to use. It's at [link|http://www.karelia.com/watson/|[link|http://www.karelia.com/watson/|http://www.karelia.com/watson/]]
(Shareware, $US30, but full-function demo is available.)
I'm just totally digging on this today for some reason.....