Lest we rest too easily, here's a potential pitfall of upgrading to Snow Leopard: some of the computer-tracking software that's designed to help you get back a stolen machine might not be working. (See "Help! I'm Being Held Captive, and All I Have Is a Wi-Fi Network!", 2008-05-23.)
Of the three most popular tracking packages, each company is either ready or nearly so for Snow Leopard. Orbicule has a new release out for Undercover for Snow Leopard, which can be downloaded and installed over an existing copy.
CompuTrace LoJack for Laptops from AbsoluteSoftware comes in Mac flavors, and the company said that its software in the current release has been tested and works with Snow Leopard. (One of the comments on this story, and email I received separately from another user confirms that.)
MacTrak from GadgetTrak, which I had installed on my work machine, isn't yet Snow Leopard compatible. I contacted the company, which says an update will be out quite soon, and registered users will be notified via email. [Update: GadgetTrak on 24-Sept-09 sent registered users email with a link to a patch that will upgrade its software to a Snow Leopard-compatible version.]
If you haven't upgraded to Snow Leopard yet, you can do so safely with LoJack; upgrade with Undercover; and sit tight until word arrives from GadgetTrak.