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

[PeterB]

Hmmm... maybe another, better question is: what will SL do for me that Leopard won't? (I'm not in a forced upgrade situation; no IT department breathing down my neck, etc...)

When I mentioned file structures -- for example, the file structures for Address Book changed between Tiger and Leopard. Likewise for Mail. So these are real concerns...