I've just tried 10mm front and 15mm rear on mine, but it's a mixed bag for me.
Yes, it looks better, and I even think the rear could take 20 or 25mm to be honest. But, the steering with just 10mm on the front is what I would describe as 'corrupted'! Basically, I thought it was pants, heavier, less precision, and just felt 'wrong'. This is on the standard 17" S3 alloys.
I'm running 10mm on the back now, but have removed the front spacers. The steering is back to how I like it, and the rears look a little less lost now too.
Im going to look at some 18" 8.5 or 9" now, so they can fill the arches more without corrupting the steering/offsets.