For whatever reason, I’ve once again been invited to the AppleSeed program and I’m running Mavericks (10.9) on my MacBook Air. A bazillion other blogs will have thoughts on the subject, I’d just like to point out that TextExpander works as long as you figure out how to enable assistive devices in the rearranged System Preferences…
Visit Security & Privacy, then select the Privacy tab. There you’ll find Accessibility, and to the right will be a list of applications that you can allow to control your computer. Enable TextExpander and all is well again.
I lived without TextExpander for an entire day before figuring this out. Thanks to treichert in the MacRumors forums.