One of the few reviews of MEPIS 7 out there: SimplyMEPIS 7.0 which was released on 23rd of December 2007, has been logically based on the immensely stable Debian Etch and will be synchronized with Debian Lenny (when it is released).
Read it here
What was Warren thinking about? Abandon the ship! I suppose Warren Woodford has some very strong reasons to adopt the Debian Etch core as the engine for SimplyMEPIS 7.0 after having explored the Ubuntu-land! SimplyMEPIS 6.0 and 6.5 were based on Ubuntu. Dapper to be more precise! The interview with Warren Woodford, the founder of MEPIS LLC by DesktopLinux.com on 30th of July 2007 brought out the reason why it was difficult to base his distribution on a non-rolling-release Linux distribution like Ubuntu Linux.