The device bits for Sync Services for ADO.NET have been released to the web so now we have a have a supported version of Sync Services for Windows Mobile 5.0 and 6.x.
You can find the download at http://www.microsoft.com/downloads/details.aspx?familyid=75FEF59F-1B5E-49BC-A21A-9EF4F34DE6FC&displaylang=en.
Keep in mind that you'll also need SQL Server Compact 3.5 Service Pack 1 for Windows Mobile at http://www.microsoft.com/downloads/details.aspx?FamilyID=fce9abbf-f807-45d6-a457-ab5615001c8f&DisplayLang=en as well as Visual Studio 2008 SP1 which can be found at http://www.microsoft.com/downloads/details.aspx?FamilyID=fbee1648-7106-44a7-9649-6d9f6d58056e&DisplayLang=en.
This sync technology is a developer-focused companion to Merge Replication that can take advantage of the more efficient change-tracking engine in SQL Server 2008.
Since it's based on a higher-level ADO.NET Provider model, you can also get it to sync your device with other databases like Oracle and DB2, Cool!!