Apple has released iMovie 10.0.2 with fixes for unspecified issues that were causing the video editor to crash. The update also fixes two sharing issues: one that would cause sharing to fail outright and another where the Share button would not respond. Other changes include fixes for instances of blank project thumbnails and high-resolution images that appeared green, plus resolution of a problem where the Crop, Ken Burns, and Map features were not accessible on Macs using certain languages. iMovie 10.0.2 now requires OS X 10.9.1 Mavericks. ($14.99 new from the Mac App Store, free update, 1.94 GB)
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).