Originally Posted by
DeathSlam
There are also cheaper paid left luggage facilities at the railway stations in town (E.g. Wein Mitte). Means carting it there and back but that's not hard.
I don't know if it is the same in Vienna, but we used the left luggage lockers in Salzburg HBF recently (which were very handy and not expensive) but there you had to pay in Euro coins, no cards or notes. You may wish to have a few coins on you just in case if you plan to leave bags there. Others might be along to correct me specifically on Vienna, however.