Harry,
You should not have to uninstall previous versions of Sync Services for ADO.NET. Sync Services for ADO.NET v1 shipped with VS 2008 and has both a run-time and designer component. The designer component (called "Local Database Cache" item) will break if you uninstall Sync Services for ADO.NET v1.
Sync Services for ADO.NET v1 installs side by side with the Microsoft Sync Framework and you should have no problems installing both on the same machine.
We will clean up the download page ASAP. Great catch!
Hope this helps
-Sean