Thanks for the great review! I'm sure this helps a lot of people who are sitting on the fence about changing springs and tires.
If comfort only suffers marginally but I get a huge improvement in handling I'd go for it. Not to mention the fact that the car looks 10x better. Like what RC said, it's a matter of personal preference and what you value more.
At the end of the day, I bought a BMW because I'll be driving the car. It's supposed to be the Ultimate Driving Machine right?