You might have noticed that I haven't really talked about text stores on this blog. That's because I've been working on an article for MSDN Magazine on just that very subject. It's in the July 2007 issue, and I just got my copy in the mail, so if you're a subscriber, you can read all the gory details about how to add TSF support to your controls and applications, complete with a working example.
The article isn't currently available online yet - I'll add a link to the article as soon as it's available.
Update: The article is now online, and you can find it here.