There are a few factors involved with running CD-Rs on the system.
One of them is the type of CD system being used. There are three categories: original CD units (PCE CD brief case model and TGCD model), the original Duo models (US or JP - the blank editions), and the last group (SuperCDROM attachment, and the Duo-R models). The last category, from my experience, pretty much plays any type of CD-R. Even the really crappy ones. The original Duo modes tend to be hit or miss on overall readability. And that leaves the original CD units, which tend to experience the most problems.
Other factors are the CD-Rs themselves. And of course the last factor being the burner. I've had good luck with DVD/CD combo burners, and I've also had bad luck with them. My laptop burns great CD-Rs, while one of my desktop Blu-ray combo burner isn't so hawt at the job. I've had burners where the lowest speed would produce "coasters", but the next speed up would burn perfectly working discs. You pretty much just have to play with it and figure out what works best.
On a side note, while I haven't done this myself, I've heard that getting a laser replacement for the original Duo models (black editions) really improves CD-R readability. And one other thing to note; there's something that seems only to appear to happen on the original Duo models: parked laser issue. It's where the unit can't read correctly from the CD-R, so it attempts to scan something at the end of the disc.. but exceeds the length it can move and gets stuck/wedged tight (it can't undo itself). You have to manually turn the axle/screw by hand to get it free. I'm not sure how common this is, but I've personally seen it happen to three different US Duos.