I've tried Princo.

For PS2 back-ups, I've noticed that they will load notably slower compared to a back-up of the same game made on a Ritek. And not just boot slower, I mean load slower. Every load. Slower. Slow. Er.
So, I don't use them for fear that they're probably killing my laser faster than normal.

As far as movie back-ups, I haven't had a good write yet. Halfway through the movie there will be a 3-4 minute segment that is garbled and near unplayable. If you hold the dvd-r up to the light you can see a ring of semi-translucency whereas the rest of the disk is fairly opaque.

Princo's, at least for my trial, suck b@lls.