The Linux Mint Debian team announced the release of LMDE 201204, which includes the MATE 1.2 default desktop environment along with Cinnamon 1.4 and Xfce 4.8 desktop options.
Because Debian isn't compatible with Ubuntu Linux, LMDE is not compatible with Ubuntu-based Linux Mint editions. According to the LMDE blog post, this new release is faster and more responsive than Ubuntu-based editions, but might be a little rough around the edges because Debian isn't quite as user-friendly as Ubuntu.
LMDE is a rolling distribution based on Debian Testing, so expect frequent updates.
The known problems in the latest LMDE include the lack of a default boot splash because Plymouth wasn't considered to be stable enough for this release. VLC won't work in Live mode, but will work after the system is installed. Also, sometimes the MATE session fails to theme itself, particularly in Live mode, so you might see "ugly looking panels and icons" instead.
Visit the Linux Mint site to download the latest release and see screenshots of the desktop options.