LMDE still has a lot of rough edges...updates are constant..where as you might get 300 or so updates in 5 months on Linux Mint main edition...you will probably get at least 300 per WEEK in LMDE...and there are opportunities for breakages of the sort you rarely would get on Main Edition...If you very techie (geeky) and love lots of fixing and tinkering to get things smooth, then LMDE will be perfect for you....
If you want pretty stable and reliable, go with Main Edition...and it is very smooth as well (unlike LMDE)...
LMDE is based on Debian Testing...so it isn't rock steady and always reliable...I used it for a few months and return to Main Edition....though it was an interesting "learning experience" i decided it wasn't for me...I'd rather have smooth, steady and reliable

Also, when installing you must be very good at manually partitioning because LMDE has no auto install options...
Just running it on live dvd won't give you a full picture of what it would be like...because it LOOKS like main edition though some of it's rougher edges will be immediately apparent...
But if you want to run it in a virtual machine, then you would get a better idea (but it will take some time to get the flavor of what it is like)...
Again, i went back to main edition...but many here love it, warts and all

It will NOT be more reliable then the ubuntu based version of Linux Mint, unless you go to debian stable but then it's not really a rolling release anymore so you might as well stay with main edition if you want stable, reliable and less "headaches"...
