personally don't like the disk dr. at all because of the ring effect it leaves on the cd/dvd you have cleaned. However, it does indeed fix the disk most of the time. Just to let you know, i'm trying to sell off my disk dr mainly because I rarely use it. If you or anyone else is interested just shoot me a p.m
I too usually have great luck with a Disk DOctor (asking for an electric one for Xmas...those hand crank ones are a pain in the ass). However, there's been a couple instances where my scratched DVDs no longer worked at all....couldn't figure it out.

As for the ring effect, it should be damn near invisible if you buff it correctly after resurfacing (or de-surfacing, as it really is).

-Rob