Thanks nekrosoft13 for the heads up on this one.
AC has released what could be considered to be a stable 4.00.40 which fully supports Detonator 27.xx on ALL operating systems.
There are no other reported or found issues.
NVmax tweaks NVidia based chipsets for maximum performance, so if you own a TNT/GeForce, get this :)
Download: NVmax 4.00.40
News source: NVmax