This is a handy way to pay one price and be able to use the transportation and many of the entrance fees on the one card. We really got our money's worth. Also, it makes it so much simpler to pay ahead and then not worry about exact change.
I found city card very useful especially if you plan to see most of the paid attractions. This even includes the Untersberg Cable car, Hellbrun palace (Trick fountain) and discount on the Hallstat salt mine
We were unable to get our card when we arrived as they were closed and we were unable to get our card in the morning before our Sound of Music tour so we ended up paying a lot in taxis and bus fare before even getting the card, so we really didn't get our money out of the card. Many of the sights closed at 5 so after out tour we got in one sight before everything closed. Not sure it was worth it.