Delphi's ECO is a great benefit in the .net world compared to Visual Studio. As far as I know there is no such thing in Visual Studio (yet) that matches the brilliance of ECO.
Until now ECO was only available in the Architect SKU of Delphi. According to the feature matrix of Borland Developer Studio 2006 ECO will be in all SKU's available.
The only difference (according the feature matrix) between the Professional and higher SKU's are that the higher SKU's have autoform support for ASP.NET and State Machines.
As a professional SKU user that is great news. Besides the above mentioned differences it seems that the professional SKU only supports basic object-relational mapping and transparent local XML persistence.
That said you can conclude that for ECO with database persistence support a higher SKU is needed.
Anyway I will definitly upgrade my Delphi version to either professional or enterprise SKU!
Still some time to decide....