My daughter and I spent a week in Vienna at the end of May. We purchased three different museum passes. The first was the Sisi ticket (around 50 euros), which included the Hofburg Imperial Apartments, the Vienna Furniture Museum (exceeded my expectations!), and Schonbrunn Palace. It saved us money, but the main reason we purchased it was because it allowed us to skip the lines at Schonbrunn Palace, which apparently are quite long. We purchased the ticket at the Furniture Museum, and there was no wait at al there. The Treasures of the Hapsburgs ticket was 29 euros and included a visit to the Hapsburg Imperial Treasury and the Kunsthistorisches Museum. The final ticket included some smaller museums - the Austrian National Library, the Globe Museum, the Papyrus Museum, and the House of Austrian History with the Ephesus Museum. We looked at the Bundesmuseen and decided that we wouldn't go to all of the included museums. The tickets we got made sense for us, and then we went to Belvedere on a regular ticket. We didn't have any lines at the end of May/beginning of June, although Schonbrunn was incredibly crowded, and we may have had to wait there without the Sisi ticket.
Look at where you plan to visit and decide whether a particular ticket makes sense for you. And have a great time! We loved Vienna - it's a museum lovers paradise!