I've taken it apart several times and must be missing something obvious, can't see what is causing the grey look (which I like)

A lot of those design elements are called as part of the Eclipse framework now.  This is why things revert back to an old R6 type design when you launch the client with the /basic switch.

As to the point about inconsistent design application, another prime example would be the template used for the PNAB.  If you have ever clicked on "Advanced" there you would notice that it looks the same as it did with Notes 6.x...

A prime reason for the old design elements to be maintained was for Domino web access to these databases and for users who needed to use the Basic client vs the Standard client.

In order to quickly give an application the new Social Edition look and feel, you need to create a Composite Application that uses the PIM (Mail) Components.
 

DeveloperWorks has a short tutorial on how to do this.
 

Once you get a handle on it, it will take you less than 10 minutes to give an old Notes application the new Social Edition look and feel.