Mojo has mentioned the M80s sound less sibilant(was that it Tex?) when the grilles are on. I haven't put the grilles on mine yet, still enjoying the look of all those drivers so I really can't comment. I have noticed that the grille cloth is now thicker than in the past. When the grilles are on my M22s/VP100 I can still see the drivers through it, but on the newer M80s/VP150 when the grilles were on, ever so briefly when they first arrived, I couldn't see the drivers.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70