I am following the 'incoming' repo path and am happy so far with what I've found - with one major exception. I cannot get Thunderbird to synchronise with my Google calendar any longer. I run Thunderbird by keeping my xxxxxxxx.default folder set with a symbolic link to a folder on my NTFS 'shared' partition. Every time, so far, that I have installed a new distro, be it coming from Mint 9 to 10, to trying out Mint 11 to Fedora and Bodhi, all I have needed to do is install 'xul-ext-lightning' from the Package Manager and the next time I fired up Thunderbird it automatically picked up all my calendar settings and resynched straight away.
However, I do not seem to be able to that under LMDE now. I don't know ifd this is something caused purely by going to 'incoming' as I haven't previously tried this on LMDE at all. 'xul-ext-lightning' isn't in the repos, the alternate showing is 'calendar-google-provider' which doesn't do the job and if I look on the Mozilla Add-Ons pages then I find both 'Provider for Google Calendar' and 'Lightning' which both require Thunderbird 5.0+.
If I have to upgrade to v5 to get my calendar back then I will do so, but I don't want to just go ahead and do it if there is another way round it as I cannot really afford to lose my calendar link which currently works fine from my Mint 10 setup.