In a very weird spot. After a successful upgrade without any hitches everything ran smoothly. Until it didn’t. Suddenly everything ground to a halt, webpages wouldn’t load. Activity monitor showed logs being written a mile a minute (some process writing to a log, whose only reference was a corrupt system install). Also the bold version of the system font showed as question marks so something was going on with the fonts. Logged in to a clean profile and everything seemed fine. Deleted the offending log files and all caches and logged in to my main account. Same issues. Cleaned my caches and reinstalled the system, seeing as that had fixed the same issue three years ago from the Apple discussion thread I found (I’ll find the process / log file I googled, something to do with symlinks). Came back to the iMac two hours later and found it in good shape, only backing up 21Gb of data to my time capsule, something that had failed in my previous install. Ah, I thought - I must just have missed that it was backing up and that’s why it was slow. But alas. As soon as I stopped (skip backup - or pause really) everything went south. Beach balls everywhere, web pages stopped loading. Had to force a restart. Fans blowing at full speed, weird things happening like getting to the login screen and then going back to the black loading bar with a stuck loader, yet operational cursor. Tried all the loading tricks, uncoupling external devices, verbose loading, recovery mode, which sometimes got me nowhere and sometimes got me to recovery mode. Disk utility failed at repairing my main disk. Right now I am installing fresh again. Never experienced anything this strange and unsettling in any of my 30 years of being a Mac user. I just hope this install will get me back to a working desktop at least :/ Anyone else having problems with this? --- Post Merged, Jun 6, 2017 --- For the record I am well aware of the risks of beta testing having run every beta going back to Copland, as well as the risks of upgrading entire file systems. Just want to see if this is a fluke or a widespread problem.