Linux Mint Debian offers the "ready to use" Linux Mint experience in a rolling release Linux distribution. Until now, LMDE was only available in 32bit, but an announcement on the Linux Mint blog states that Linux Mint Debian 64bit will be released in December.
Besides a 64bit version, there are other "goodies" that are going to be available in the new Linux Mint Debian release (if you're using the 32bit version, there's obviously no need for a clean install - since it's a rolling release, all you have to do is upgrade your packages): improvements to the installer, fonts and sound as well as performance tweaks such as the now very well known 4 lines alternative to the "200 lines Linux Kernel patch that does wonders".
[via Linux Mint blog]