From my experience, Apple is using +-R drives in their PowerBook and Power Mac line and just -R in the iBooks, iMacs and eMacs. I'm pretty sure about this.
I'm referring to new, current models. In the Power Mac G5 and 15" PowerBook you can use +R media. (All Macs support -R, Apple's Official Media) I assume the same with 12" PowerBook, but it might be different.
The current 17" iMac, SuperDrive eMac and 12" iBook do not work with +R.
Q: What about the Powerbook's released after September 2003? (the Aluminum 15" and the newer 1 ghz 12" and 1.33 ghz 17" pb)?
A: This drive comes with the UJ-816, which already supports 2x dvd-r and 1x dvd-rw, as well as 16x cd-r. Therefore, this firmware is unnecessary on this version of the powerbook superdrive.
"The SuperDrive (DVD-R/CD-RW) lets you read and burn music and data CDs, as well as DVDs that can be played in most consumer DVD players. The SuperDrive plays DVD movies — the kind you buy or rent — and writes to 4.7-gigabyte DVD-R discs, and it reads CDs and writes to CD-R and CD-RW disks."