I bought the new PPaint and tinkered a bit with it. The new toolbar is nice and makes drawing in very high res possible. The second row of brushes has wrong colors in the toolbar and is invisible. Could be fixed easily.
But what is "full Workbench integration" supposed to be? The lack of updated documentation (still at 7.1) does not help here.
Btw.: Icon startup type is set to shell, should be Workbench.