Snow Leopard Exchange support isn’t quite as good as it looks. The email works well, but contacts show up in their own separate folder. You can’t sync them to your normally contacts on your mac. This means you can’t sync them with Mobile Me and they often are available in other programs that use your address book. Calendar support works the same way.
It is a step forward, but not quite what a lot of people were expecting. Still the mail working well is a great thing. In the past messages would disappear and reappear when connected to an Exchange server and that doesn’t seem to be a problem with this version.