Ahhh I forgot to mention....

With 10,000+ shares (approximately) windows NT4, Windows 2000, (and probably win .NET) blue screens, because the size of the .system registry file becomes too big to load into memory when the server boots up (16mb limit for registry and kernel at that point - yes shit i know!)

So i've had to use DFS, hence can't use the "oldest trick in the book", but thank you anyway!!