Despite the fact that it's a chain, (this) Mokador gets five stars because it consistently delivers…read moretasty, unburnt cappuccinos, and their non-smoking section is stellar. You do have to walk through the smoking section to get there, unfortunately, but that's pretty standard, and here the non-smoking section is closed off, so it's truly without smoke. It's also just a nice room, always clean and quiet, and the service is great by Vienna standards.
Mokador has free Internet, and supposedly iPads you can use while you're here.
In the summertime they have outdoor seating and frappes, which are usually not sweetened at all (even when they are already sweetened, I find it to be not overly so). I've had snacks here, like sandwiches and cake, and that's always been tasty, too.
And, perhaps most importantly, the water served with your coffee (even iced coffee) is sparkling mineral water, which to me is just the icing on the cake. A nice place with great prices, and if you need to use the Internet and/or study, the non-smoking section is ideal.