I successfully beta tested High Sierra for several weeks, then High Sierra went bonkers starting with the next to last Beta version prior to release. It bricked my system (had to go back to 10.12 and had to reconstruct from scratch). The released 10.13 has yet to be successfully installed on my iMac (late 2012). I first tried the released version on my internal Fusion Drive (gave up on that, when it tanked similar to the failed beta release that I mentioned above - had to rebuild again). Next, I built (2) external Seagate HD's with 10.12 (given the advertised issues from Apple, concerning Fusion Drives) and just tried both of them as opposed to the Internal Fusion Drive (They both fail repeatedly). I reloaded the 10.13 update from scratch and experienced the same failure. I've been an Apple Fan/User since the 80's - This is the biggest disappointment (I removed the expletives) I've ever seen from Apple - It's ridiculous! I guess I'm destined to not being able to update hence forth. Very Sad.