The service pack release includes a number of new features, perhaps the most valuable of which is the addition of the Serializable attribute. Rodel E. Dagumampan also pointed out that this will allow him to reuse his CF classes for web services. Matt Hamilton is also excited about the ObjectDisposedException bug fixed in HttpWebRequest, which should keep his mobile app from crashing inexplicably on exit. This bug was happening in certain applications using asynchronous requests.
This release also includes a new utility called the .Net Compact Framework Remote Performance Monitor (RPM), which gives you a real-time graphical view of your performance statistics. Steven Pratschner has blogged more details about the tool.