I've removed the stickers from both the X5 and the M3 and a 335i using acetone.
Use the kind found in the paint store. I don't think finger nail polish remover is strong enough.
Remove the visors as mentioned above.
Wear gloves to prevent your hands from the acetone
Saturate a clean cotton rag and place it on the decal. I worked on a small portion at a time. After about 15 seconds the sticker will begin to dissolve and can be gently rubbed off.
I followed up with some Goof Off cleaner to remove any adhesive residue followed by some 303 protectant.
There is no trace that the stickers were ever there.
If you leave the acetone on to long or rub too hard the plastic will soften little and possibly get some waviness to it. This happened to one of my visors. However after a few days the plastic stretched back into place without any adverse effects.