Honestly, I can't think of anything I need that Thunderbird doesn't do. IMAP support? Yup, and the offline support works great too. Search got awesome in the new version. Calendar is supported with Lightning, and works well with Google Calendar. Multiple languages and encodings? Also just works.<p>So what if it can also be used by non-technical people? If you want something with more geek cred, set up emacs to do your email. Otherwise just write an extension to Thunderbird that implements whatever functionality it's currently missing. There is no need for more fragmentation.