Thanks everyone!
Jacob's note stepped me through the RoR screencast's actions* Alan's note lead me to the TextMate screencast which starts to unlock TextMate's bundle and snippet secrets* And Tom pointed out that I was seeing snippets in use, not really completion.
If these answers lead to a new question its: does TextMate have all its features when run in Panther (OS X 10.3)? And if not, what am I missing? Scrutinizing the text insertion screencast I noticed *my version (1.5.3) is missing the "Automation" menu. Ah-ha!
I find no mention of system requirements or Panther versus Tiger capabilities in the docs (aside from a couple minor ones). Is there a version feature comparison matrix somewhere? Maybe that's just for when you have an entire martketing department!
So, thanks for all the help,
Ivy