I read that this card offers fast-lane access to museums and reduced rates for vaporetti. Has anyone had an experience with buying and using the card?
The current version of the Venice card is a museum pass only. It does not offer discounts on the vaporetto. For that you need a separate Travelcard, which comes in increments of 12 hours, 24 hours, 3 days, and 7 days. The 7-day pass costs €50. Considering that individual vaporetto tickets cost €7, that is a bargain if you plan to ride the boats a lot. However, we spent a whole month in Venice and just bought one 24-hour pass, consolidating our trips to the outer islands into that time frame. Otherwise we enjoyed walking everywhere.
Rick's guidebook coverage of Venice suggests that it's hard to make the Venice Card pay for itself (40 euros to cover 11 city-run museums and 16 churches). Smaller options include a Doge's Palace & Correr Museum Combo ticket for 12 euros (buy at Correr to skip the line at Doge's Palace) or a Museum Pass for 24 euros (doesn't cover the churches, which cost about 3 euros each).