So I decided to test the Cap on my external usb 3 enclosure. Downloaded the first public beta from the App Store, double clicked, selected the partition (GPT HFS+) restart. Now when the installer boots up, theres nothing writing or reading my external, and after not even a minute it unmounts, only option for install is my Yosemite installation. I even ran a diskutil verify on terminal just to see if I could keep it busy, and it actually unmounted midway, so I decided not to try that with the installation. Couple of things to note: -There was no USB tab in system information in the OS X install. -A week ago I installed El Cap to a usb 2.0 stick, no problems ( just painfully slow) -On this same external enclosure I have 2 other partitions, one is for Time Machine the other for stuff I dont want in the TM, no filevault. -The external works fine in Yosemite, stays mounted even if disk spins down. -This is the first public beta installer, should I download the latest? Does the installer use actual beta drivers and maybe theres a buggy one for usb 3 ???