Product reasonably easy to apply. Get a slightly damp sponge (or soft brush of your choice), spray the foam on, work it in. Let sit for 10-15 mins, damp sponge again (hopefully with a clean one =P), and then vacuum.

Results:

S4 Onyx floor mats, stained with Starbucks Chai Latte foam - No trace of anything left on mat. Cleaned 100% for 15 minutes of my time.

BMW Sand floor mats, stained with general wet-weather stuff over a year - Still some traces of dirt. A second application would most likely take that out.

All in all, pretty nice. Your mats don't get soaked through, and it does an excellent job. I'll try to update this when I try the acid test: the sunroof headliner in my old 325.