OK, I just double checked that with the NEC Japan site, that says it's compatible with both - and +R DL.
The plot thickens... :eek:
Edit: OK, the more I'm seeing, the more apparent it's becoming that it supports both - and +R DL.
If you have that burner, check in Nero InfoTool (in the Toolkit), that should tell you definitely if it does or doesn't do DL. There should be a check in the +R DL and -R DL boxes.