I have visited Austria many times, on my own with my wife and also thanks to a friend who was stationed there for a few years. Vienna is such a lovely city, and I got to see one of my favorite paintings (maybe my most favorite painting, really), Gustave Klimt's The Kiss, in person at Belvedere. My aunt lives a number of hours away from Vienna so I never got to see her there, so a return trip is not out of the question!
I regularly take friends and family visiting Vienna to see The Kiss, its a common waypoint in our tours of the city. Glad you love the city, it is indeed a very fun place to live .. although, in some ways, a bit like a small country town.