I noted that existing contacts (before initial sync) on the Mobile (in my case a Nokia E71, Mail for Exchange 3.0) are not getting synced to GroupWise.
According to the log on the mobile they were synced to the Data Synchronizer, but from there not to GroupWise.
Creating a new contact syncs fine.
Modifying a previously existing contact reports a sync on the mobile, but nothing in GroupWise.

It might not be the regular case to do a inital sync more from mobile to GW but if a user is added the first time with a lot of contacts in his mobile and would like to have them in GroupWise it would be cool if it works...