I bought 100 of them, and have used them when I wanted a show to fit on a disc and it was over 83 min or so. I have never had an issue playing them on any machine, even some very old cd players, but I am sure that some machines will not like them.
It is kinda like super overburn. I have not had problems with overburn either, but I usually set my recorder for a minute or so more than I really need when overburning. I am not sure if this is good or bad, but It seems to work fine for me. Obviously with a 90 min CDR, it is like the overburn is set automatically for 10 extra minutes. I don't think the disc is significantly different than an 80 min CDR. They do seem to be a high quality CDR though. Here is some web info:
90 Min CD-R FAQ
Q: Why does my burner recognize 90 minutes CD-R as 80 minutes CD-R?
A: A standard CD-R is capable of recording 80 min of audio or 700MB of data, until recently a new 90-99 min format has been developed utilizing "Overburn"; however because Overburn feature is not standardized feature offered on all CD-RW burner in the market, not all CD Burner can recognize the extra storage space present on the disc. To be able to used the extra 10-20 min of extra recording space, you need to have a supporting hardware and software and the correct software setting.
Q: My burner manual shows compatibility with 90 min CD-R, however the burner is still recognizing the media as regular 80 minutes CD-R?
A: Most CD/DVD Burning software has limited the recording size to protect the burner that does not support 90 minutes burning. Therefore, most software disabled the "Overburning" feature by default. To enable this feature, go into the software preferences / setting or configuration and find the "Overburning" setting and set the maximum to 90 Minutes