Thanks everyone for the great information and discussion. Love this forum -- can always rely on a post to help make an informed decision! After reading all your posts and seeing all your photos I have decided not to tint. My M3 is really mostly a summer car for me and I prefer to use it only when the top is down. On the occasion when I do need to drive it in the winter it is usually at night and on occasion in bad weather. I don't think the tints are a great idea for visibility.
Above all, I don't like the tints on a white car with the black vert top. To me the car looks very clean as is and there is something beautiful about the stock M3. The tints scream that the car has mods (whether true or not), which I appreciate on others cars, but I think I like the look of mine as is.
SO I'll be dropping the car off to MNC Auto this week for BSW Stage 1 and pass through sub upgrades and some other tune-ups but I won't be tinting, for now at least. Thanks again, all!