Late to the party, upgrading from Leopard to the snowy cat, what do I need to know?

[Gareth]

For a variety of reasons, 10.6 isn't working out for me. I'm going back to 10.5 this weekend. It's probably partly my fault for using the 10.6 upgrade to fix a hosed 10.5 system, but since I still use Rosetta, I don't see the point in using 10.6.