I guess I'm super unlucky because every time I've been to Mozart's there's always a super long line at the coffee bar, the desserts somehow always end up costing me an arm and a leg and aren't that great (I've tried the choc. mousse, keylime pie and blueberry cheesecake...didn't finish any of 'em) - you have to agree that a non-generous slice of dessert at almost $6 is a bit steep for a casual coffee shop.
I have to agree the coffee is very good, probably because of the fresh roasted beans (they roast their own) and the patios are very spacious and have live music on the weekends.
Great place to take friends, family, dates, etc. and the views are the better than any other coffee place in Austin (unless you go to the Oasis for coffee).