Apple's new OS Maverick is out and I've had several reports from photographer friends and our software customers that it is not always playing nice with Photoshop. If you are in them middle of crunch time, trying to get your customer images out on time, you may want to wait just a bit before upgrading.
If you do want to upgrade, make sure to have your time machine backup up-to-date, or use some other backup software that makes full, bootable backups – so you can revert easily if the upgrade doesn't go so smooth. SuperDuper and Carbon Copy Cloner are two long-standing favorites in the Mac community.
Do a full backup of your computer, then update to Maverick, and test. If it doesn't work well, restore from your backup before creating any major amount of work on the new system (or you'll have to re-do that too when you restore the old backup).
Better yet, hold off a while until Apple or Adobe release updates to address the issues. Giddy-up!