Today I continued on to the next developer preview and it is great. Much faster...etc, you all know. Anyway, in the last two hours I've had a weird problem where my 2012 rMBP would hang, produce a Beachball, and freeze. The cursor would still move, but even after 20 minutes I had no obvious signs of returning from beyond... So I forced the computer to shut off, rebooted and was confronted with the error that I was running out of disk space. I checked and saw that I only had 2GB of space... Which was weird since I had about 150GB earlier today. I remembered reading a thread on here a few weeks back about something similar and went ahead a repaired disk permissions expecting to find some small glitch and return to normal operation. It did... for about 3 minutes. Used Internet Recovery to repair disk; repaired permissions again; found I had 150GB free, then few minutes later it warned about disk space again; used GrandPerspective to view all files to locate a runaway log file - nope... Is this a symptom of a failing SSD? I'm going to backup and restore to Mavericks tomorrow just to test this theory. Shout out to Carbon Copy Cloner for making it easy. Thought? Thanks. P.S. Just happened again.. posting now! Edit Just performed the same routine... Laptop crashed, etc. However, I noticed Kernal Task has written 10GB in the past 10 minutes... In Activity Monitor what is normal under Disk? #2 Edit: See this link: https://www.youtube.com/watch?v=d1IUU_bsWrc&list=UUOHNCIJhS-5_e6zuDhTTlGA Notice the Finder Status bar under Activity Monitor, when it gets low in space, the computer freezes. Thus far I removed about 40GB of things I knew I had a backup of. I'll Firewire Target disk mode backup everything else tomorrow. Thanks again!