I don't know how dark mine are either since the dealer did it before I even looked at the car. I'm guessing around 25%. They're pretty freakin' dark, but I like it.
The only other things I've seen people do are shift knobs, painted OEM rims, and the alloy pedals (as shown in this thread). The aftermarket needs to hurry up!
I have done a few other things to my 2010. Here's the current list:
Bronze OEM 17's
Red calipers
25% tint
Fiamm low-tone horn
Racing Beat RSB (first gen, but it fits)
DIY 36-LED 3rd brake light
I wanted to get the moonroof wind deflector cause i like the way they look and i'm a smoker too, do you guys know what kind of install kit there is with the genuine mazda part?