Well, I've been running Yosemite for a little less than a week. I just got over the ridiculous iPhoto problem with .NEF files but smooth sailing since then. I was in the middle of using the computer and it suddenly went to a gray screen and rebooted like a kernel panic without it explicitly stating it was a kernel panic. Now it takes forever to boot and never does get to the finder. If I do a command-r at boot I can get to the recovery partition and when attempting a disk repair I get: Verify and repair volume "Macintosh HD" Repairing File System File System check exit code is 8. Updating boot support partitions for the volume as required. Error: Disk Utility can't repair this disk - back up as many of your files as possible, and restore your backed-up files. UGH. I can't mount the drive to back any data up (I have most of the data, just not all of it). This OS is the buggiest yet. This drive was replaced under Apple's program in 2013 for recalled Seagate hard drives. Looks like the drive is iffy or the OS is iffy. I found a blogger that ran in to this issue and he just nuked the internal drive and started from scratch but I'd prefer not to do that. I was hoping to recover some additional data - anyone have any additional recommendations?