I have Audi's sat nav that happened to be fitted to a 2nd hand A3 I acquired. Also agree it's nowhere near as good as, in my case, Google Maps on a phone. I've seen odder routing, less effective traffic avoidance, and the voice control of Google Maps is awesome - tell it to "Navigate to xyz" and you have the power of Google behind it to find and direct you the place you actually intended to go :). I appreciate Google and their services aren't liked by some.
I was, however, amused in the dealership when looking at another A3 without Sat Nav, that the Nav key is still of course present on the center console and if you press it you get a message that Nav isn't installed - like a permanent reminder from Audi it was an option you chose NOT to buy on your new car . Having said that, it's probably not an option I'd have chosen for the price - it's one of those technologies that's advancing rapidly enough to be better via a constantly updated app on a phone, in my opinion.