I decided to give LMDE a try last night. I had never used debian or a 100% debian compatible distro before so I didn't quite know what to expect. So far I am absolutely loving it. I have always been a fan of the rolling release model, its what I really liked about arch. LMDE is certainly missing some of the nice touches ubuntu has making things more streamlined, but I found it wasn't much harder to setup and the performance and stability of LMDE more than makes up for it.
I have always had performance issues with ubuntu/ubuntu derivatives, my biggest pet peeve is when compiz is enabled smooth scrolling in every web browser was horribly laggy (using both the oss ati drivers and catalyst 11.3/11.4), and compiz's performance in general disappointing (slightly laggy minimize animations, white flickers during fade animations. In LMDE scrolling is just as smooth as in windows, no lag. All animations are totally smooth and artifact free. LMDE boots faster, feels more responsive, applications launch faster, and uses less memory. LMDE also comes with every program and codec I need out of the box .
Also unity's gnome 2 is the best I've ever used mintmenu is awesome, the theme is beautiful and easy on the eyes, and the custom faenza based icon set is just perfect. I like it better than natty's gnome 2 and unity interface.
While LMDE could still certainly use some work in areas I think I have found my new favorite distro.