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.
The thing that keeps me on Entourage is the ability to create server-side filters. I don’t see a way to do this in Apple Mail yet, but I can’t rely on having a fat client running somewhere all the time to handle filters. I need it to keep my inbox reasonable when I’m using a mobile device.
I think you may be able to set the server side filters using OWA (outlook web access). Alternatively you can set the server side filters using Entourage and then use Mail to use your mail on a daily basis. Of course if you use Entourage regularly and are happy with it, there may not be much reason to change. I like the way that Mail handles multiple email accounts which is one of the main reasons I use it.