As often is the case we're left scrambling for release notes. But we do have an entire blog post from the Google Mobile team to go by.
Google Maps for mobile has long allowed you to add stars on a map to mark your favorite places. You may have noticed a few months ago that Google Maps for desktop browsers introduced the ability to star places as well. Unfortunately, there was no way to keep these starred places in sync with Google Maps on your phone. With today's release of Google Maps for mobile 3.3 on Windows Mobile and Symbian phones, you'll now be able to keep the starred places on your phone and on your computer completely synchronized.
For users upgrading from an older version of Google Maps for mobile, you'll be asked, when you log in, whether you'd like to synchronize your existing starred items with your Google Account. This means you can preserve all the work you've put into customizing your map on your mobile, and have it show up, conveniently, in Google Maps in your desktop browser.
Get the CAB file here for the latest version of Google Maps for Windows Mobile.