The best OS I had run to date was Mint 10 Julia (Gnome edition). I must admit I kept it going on one of my PCs long beyond its support-end date, manually updating Firefox and Thunderbird as necessary. But the time came when I had to change and I recently installed the 64-bit version of Mint 13 MATE. This time, I decided to go for a LTS edition - when I first installed Mint 10 I hadn't realised the advantages of choosing LTS in terms of minimising re-installs.
After working it hard for c. 2 weeks now, I can honestly say I'm very happy with it. It is not quite as responsive as Mint 10 was (especially on startup) but I found switching off Zeitgeist from the services running on startup improved things. Everything still seems beautifully clean, stable and easy to maintain. I enabled the Trinity repos to let me install a small handful of KDE3 apps that I still find very handy, and now everything is great.
I am sure this Mint edition will be finding its way onto a few other computers in my family over the coming days!
I know this has been mentioned before but I do feel the Download page on the Mint website could do more to highlight the LTS editions, especially as Ubuntu's support for the releases in between is now so brief. Surely LTS versions with backports enabled would be fine for the great majority of users who are not actively interested in the newest stuff, and can be run for so much longer without re-installation.