The problem I had initially with Things is that currently, it does not have any sort of support for sharing its library and configuration across multiple computers. This can be overcome using a Dropbox folder as an alternate library location as documented in this DropboxSync wiki. This is great but still leaves one large problem in my mind – Things only seems to write its data to disk when it quits. If you make some changes but forget to quit Things, then open it up on a different computer, you’re probably going to lose some data. I just found a potential solution to this problem: automatically quit Things any time your computer goes idle. Hopefully you haven’t already logged into another machine and launched Things before this happens, and all your data will be safe. I found a nice little open-source project that seems to handle this perfectly: ScriptSaver.ScriptSaver installs as a screensaver and lets you select an AppleScript file to automatically run any time the screensaver is activated. It also gives you an option to then launch a different screensaver after the AppleScript has been launched. A simple AppleScript to quit Things:
tell application Things quit end tell
Paste that into AppleScript Editor and save it somewhere; then point ScriptSaver to that file and you should be set.