I'm in love with BDC, the universal data connector of MOSS 2007. Almost any datasource can be registered in Sharepoint and pretty much used as a "native" List. That's fine and dany as long as one uses pre-existing datasources.
What if would like to use BDC to generate tables to a new datasource like SQL Server?
Well, one can sort of extract the Lists to Access 2007 and then upgrade to SQL Server, but then some datatypes are lost in the transition. If there is one thing MOSS 2007 misses is the the possibility to "use" BDC to generate/map to a new table to a new DB. Lets' say a way to save/map a List in Sharepoint to a new table in SQL Server 2005. Sometimes the Sharepoint storage engine is perhaps too much, or metadata is not used, so that a simple SQL Server 2005 table would be more appropriate. Sometimes, like in my case, I'd want the storage engine to be SQL Server and Sharepoint to be the UI/Web Interface, to keep my data/relational model intact but without losing the special "columns" datatypes of MOSS.