I was able to import all of my vital files (tens of thousands of saved emails going bavk to 1998), address book, and settings from OE. There are a few new things to learn and different ways of doing things, but in general it was a smooth transition. My old junk mail filter rules didn't come through, but Thunderbird has better tools for dealing with junk mail than Outlook Express and I'll be getting up to speed on using them shortly. Hopefully I won't find a reason to go back.