Kate, it's becoming evident that Mavericks is one of Apple's sloppiest releases ever. They released a quick Mail fix recently, but there are a ton of stability problems that people are encountering, from System Pref freezes to inability to shut down or log out, to finder windows not populating... I'm pulling my hair out with many of those and with InDesign being sluggish (though Illustrator is unaffected and Photoshop runs way faster).

Apple is supposedly beta testing 10.9.1, and AFAIC, they can't get it out fast enough.