You might want to hold off a little while before upgrading, at least until 10.6.1. I upgraded my laptop 3 days ago and since then I've had at least 5 Mail.app crashes, finder a couple of times, and one terminal crash. I did an upgrade install, maybe a clean one is better, but I'm pretty surprised at the instability.
Also, if you use Macports, that's not up to speed yet so you'll be doing a lot of fiddling around to get that working. For example, I had to patch the port for Erlang to get that to install on 10.6, there's probably others. Wait a few weeks and that should all be sorted out for you.