They're strictly for looks for 99.99% of enthusiasts.
As for using OEM M3 front setup, we tried that on my car but it didn't work. Something about how the M3 control arm not mounting to the knuckle? I can't remember. Maybe someone more technical can chime in for me.
Imola Red / Imola Red ///M5
E60 SSK, Dice iPod, Illuminated ZHP knob, MKIV, Euro Armrest, GT ExhaustDaily:
BCR Coilovers, 19x10 + 19x11 Rial Daytona Race, Michelin Pilot Super Sport
'04 E55 AMG Brilliant Silver on Anthracite leather
'96 318i Alpine White on Black
'01 330Ci Titanium Silver on Coral Red
'96 328i Jet Black on Black