I honestly don't think that I could use a Mac without TextExpander anymore. I have a customized list of "frequently misspelled words" that I have it correct for me, as well as a snippet of text for creating a new shell script, a shortcut to insert the current date or time, HTML markup, and more.
TextExpander has been able to sync via MobileMe for some time, but version 3 also includes the ability to sync via Dropbox. It can also correct "double caps" at the beginning of a sentence which happen when you accidentally hold down the shift key for too long. There is a feature to capitalize new sentences as well, but that feature was a little hit-or-miss for me.
In its new application form, TextExpander has to be running for it to work. That may seem obvious, but since it used to be a preference pane, users may be used to it running "hidden" as a daemon in the background. There is an option to hide the application icon in the dock. If you hide it in the dock, you can still access TextExpander from its icon in the menu bar. They've even included several different styles of icon for the menu bar, which is good news for those of you who believe that menu bar items should only be black and white.
The menu bar offers a slew of cool new features, including a search function and a list of all of the folders and snippets for you to navigate, in case you have forgotten a shortcut. This is a good reason to start sorting snippets into "Groups" which were previously a bit of a pain because you had to tell each group to sync via MobileMe. Syncing is now an "all or nothing" option.
You can also create a new snippet, edit the last expanded snippet (handy if you realize that you need to "tweak" it), or use the clipboard to make a new snippet. New in this version is also the avility to create global "hotkeys" which will reduce the "friction" involved in making a new shortcut. I know I've previously thought "Oh, I ought to make a shortcut for this" but I usually wait too long before I finally get sick of re-typing it and actually do it.
I've only just started playing with this new version, but it looks like a great upgrade to what was already a full-featured application.
TextExpander costs $34.95, but they offer a full-featured demo and a 90-day guarantee which is far longer than I'm used to seeing for software. If you own an earlier version of TextExpander you can upgrade for $15. Those who bought TextExpander on or after November 1st, 2009 are eligible for a free upgrade.
There's even a companion application for the iPhone and iPod touch called TextExpander touch which will sync to your local Mac, so you can use your snippets in a wide range of iPhone apps.