Hi Vince,
You are right; the sync designer in VS 2008 does not support Sync Services 2.0. In general, VS does not support products that are in early beta and subject to change which is the case here.
If you are building offline app, using client and server provider; then you might just go back to v1 and use the sync designer. Sync Services v2 does not have any changes for this scenario (except some name changes ..etc)
If you are building sharing\collaboration app, using peer provider, then your only option, at this point, is to use the samples shipped with v2.
Thanks