I've got an orange converter for my cd-r and it works without a hitch in 10.1. Of course, 10.1 doesn't support scsi burning so I'm SOL in that regard, but I hope that will change shortly. But, I can even use my CD-R drive to BOOT my computer into OS X. I'm not sure how that works out because OS 9 needs extensions for the converter... I haven't had any experience with using it for scanners, etc but I can vouch that they work fine for CD-R drives...
Something to remember when you're buying one: the orange converter is not daisy chainable (maybe if it's at the end of the chain it would work but I haven't tried) and I think some of the newer ones are. Also, some come with more than one firewire port. My converter is one of the first to come out (August of last year) so it's limited in it what it can do, but it does that exceptionally well. HTH