Hindsight is always 20/20, eh?
Passes of any kind are only a bargain if you have the time you use them, and are interested in the attractions they cover. We always do the following when considering those:
• Make a list of what we want to see
• Add up cost of individual entry fees to those attractions
• Consider how many attractions we can actually see in the number of days we have
Most passes incude all sorts of things we're not interested in and/or don't have time to fit into the itinerary without running around like headless chickens. I will say, however, that the Paris Museum Pass ended up to be a good value for us, and we more than broke even on our 6-day pass during our week in the city. A Friends Of The Uffizi membership also worked well for us in Florence. But again, I did the math in advance.
We have never purchased passes which include public transit as we would never get the value out of those: we don't take public transit enough times in a day/week to justify the cost. Free museum days? We tend to avoid those as the most-visited museums are usually mobbed on those days.
Anyway, doing the math in advance and being realistic about the time you have are key when considering passes, and may help you avoid some buyer's remorse next time?