Ok , maybe I am exaggerating a little. But still it's frustrating and searching the internet I am not the only one with this problem. Anyway I went back to Yosemite and all is well again so I regretted upgrading and that is the title of this thread since I started it.I wouldn't go so far to say it's not ready for main stream. Just because YOUR external DVD drive doesn't work 100% of the time, doesn't mean it's the same for everyone else. Granted I don't have an external bluray drive, as I replaced my internal DVD drive with a bluray drive in my late 2011 MBP, but I think you're over exaggerating your statement just a little.