This morning, the first thread I clicked on at Search Engine Watch Forums was named Google shows different titles depending on search term used. It is true, and its a pretty significant change on Google's part.
For example, do a search on rustybrick at Google and you should see:
If you change the search to rustybrick web, you get the normal, programmed title, which looks like:
The theory is that if the search matches the ODP listing, it will show it. So in my case, if you view the Google Directory (uses ODP) in the /Computers/Internet/Web_Design_and_Development/Designers/Full_Service/R/ section, and look at the 10th listing, you will see "RustyBrick" and the description. Both used in the main SERPs at Google when search on at Google, under "rustybrick".
There is an additional thread on this topic at SEW forums, named Meta descriptions displayed in Google results?