My fresh installation (just updated to UP7 with a bit of help from the forums here) will mount USB memory sticks, but will not mount DVDs or CDs, not even the DVD I installed from. I haven't tried to burn one yet, though Brasero does seem to see that there is a DVD burner present.
ISTR that some distros have a specific control panel to handle removable devices, but can't find the equivalent here.
MikeC
ADDITION 10/2/13:
Turns out that my LMDE XFCE box is also refusing to mount DVDs after applying UP7.
This makes me rather cross.

ADDITION ON 10/5/13:
It turns out that if I have a disk in the drive at bootup/login, it will be seen and mounted on the desktop normally; if I right-click to eject it, however, then no subsequent disks will be seen.