I went from another distro (based on LMDE) that the ISO uses only UPack4 and I upgraded to UPack 6 (from ISO install) with out issue (that I know of ) It also used Icewm (WM) and I changed to Xfce (prefference).
Yeah, the reason I never got around to doing the update from UP4 to UP5 is because I installed LMDE using encryption and LVM. This complicated my old way of doing backups with Clonezilla that was very easy. In principle Clonezilla should be able to handle LVM and encryption. In practice I couldn't figure it out and it seems others more advanced than me could not get it to work either.
So I was trying to find another way to do a clone/backup. The combination of LVM and encryption makes it a bit difficult. I finally settled on using fsarchiver but then never got around to figuring it out. So I guess I better do that before I find myself looking at an upgrade from UP4 to UP7.