I've done something with this beta that I don't ever recall doing with an OS Beta release before - I've made it my main OS on my Mac Pro. I'm leaving my MBA at 10.10.4. (I have 8 internal storage devices (4 SSDs, 3 HDDs and 1 SSHD) so I can readily switch OS's as I desire. I have a MVC modified Gigabyte GTX780. But, my card has revision A of the GK110. This means, unlike later GPUs) it will operate with Apple's drivers. It did slow up a bit until the Nvidia Beta driver came out. But, at least for me, having revision A of the chip is a godsend. Any way, for me, El Cap has very few bugs and is is working for me. I'm now on PB3. My issues so far. 1. I sometimes get a panic on startup or on a restart, the machine then restarts on it's own and all is good. This happened about 90% of the time on PB1 and half the time on PB2. I have not have enough time in PB3 to form an opinion. 2. Safari is a mixed bag. It feels faster, but has problems with some web sites. eBay and PayPal to name a couple. And there is an issue on this forum. When I try to upload a file I get a "Plug-in Failure" error. To upload I need to use Firefox. Not sure yet if I'll default to Firefox or not. 3. An old program I use called "Imprint" did not work at first, but is working fine now. TechTool Pro 8 is still not working. Apple's Calender is still not working. Microsoft's calendar in Outlook is working fine however.