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.
I've been using it for a week on a 1st gen MBP (32 bit) and haven't had any crashes.
I don't use Erlang, but I have a lot of packages from MacPorts (mysql5, mercurial, git, svn, xorg, perl5 and python26 ) installed without any problems. The only thing I've tried to build that failed is screen.
I did a clean install, so that may be the difference maker.
Could your instability be attributed to the fact that you might not be running the actual release version (or has been modified in some nefarious way)?
I should have mentioned that I also had the md5 of the release image. Needless to say, I verified it. There is no practical possibility that it is not bit-for-bit identical to the retail version.
I checked the file in the same way you would ascertain a Linux iso you downloaded from an unknown source over the internet is genuine. There is no doubt whatsoever about its origin and authenticity.
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.