If you are an AppExchange partner, you can join the Spring ’08 pre-release program. The nice thing about how Salesforce is approaching it this time is that you can have one of your developer orgs cloned to a pre-release server. This allows you to really see how your own configuration will be affected by the new release.
The steps to do it are easy. Go to http://wiki.apexdevnet.com/index.php/Early_Access_Program to learn more.