CAML query to select items assigned to current user.
So after much googling and trying all the suggestions at
http://forums.msdn.microsoft.com/en-US/sharepointworkflow/thread/e8891d49-1d82-422e-8c7f-eb99326ec14c
We found the way to select from a list where the Assigned To user is the current user by building a view that has a filter criteria of Assigned To = [Me]. From this we got a reference to the SPView object for that view and then looked at the .Query specified:
Our resulting code:
SPQuery qry;
qry.Query = "<Where><Eq><FieldRef Name=\"AssignedTo\" /><Value Type=\"Integer\"><UserID Type=\"Integer\" /></Value></Eq></Where>";
Hope this helps someone else save the hours we spent.