Before I discuss the previous post with the weird flipping images (BTW, did you right click the image to see you could view other pictures as well? even when you know somethings changings its hard to find it)
I tried Thunderbird yesterday as a replacement for outlook 2007. I have to say, its really good! Well, mostly importantly its fast and snappy where as outlook was slow and sluggish.
Thuderbird also imported all my email which was divided across many psts to try and get outlook to be snappy..... However Thunderbird deals very gracefully with the gigs of emails I have.
I also installed "Lightning" which is a Calendar plugin which integrates into thunderbird. Its looks pretty good, not quite as good as outlooks, but it does the job.
It also has Theming support, so I downloaded a theme called "Noia 2.0 eXtreme" and the whole thing looks reasonablly pretty (though not as polished as outlook)
I also had to muck around with a few options. Oddly enough Tools->Options didnt have a lot of the options I wanted, it was Tools->Account Settings that has lots of options.
Also the built in RSS feeder works much better with Screwturns RSS updates of wiki pages than Outlook.
It's only day 2, but so far so good. Quick fast email is such a joy! :)