iAmsterdam vs Museumkaart
In many of the tourist guides and brochures, you will see a lot of promotion for the "iAmsterdam" card which gives you a free pass to most of the major museums and some attractions in Amsterdam and includes a transport pass for the Metro and trams. You can purchase one that covers 24, 48 or 72 hours. The top cost at the moment is 58 euros for the three day card. You can also get a Museumkaart that is almost the same thing, allowing entry into most of the same major museums. The cost is, with fees, about 40 euro and it's good for a full year. There is no transport included.
What i find is that the short term cards find you rushing from museum to museum to attraction to fit everything in so that you can say you broke even or saved money. In up to three days, that's a lot of overload. You don't end up doing anything else aside from going in and out of museums, churches etc. The iAmsterdam card also gives you discounts on other things like canal cruises and some restaurants so that's also good but there are plenty of cheaper, less known places to eat or shop that will be cheaper anyway.
In my opinion, i think the museum card is the better deal because it's good for a year. There's no rush to see everything and the real advantage is that it's good at museums and sites all over The Netherlands so if you're doing day trips or traveling around, it'll save you a lot of money.
Of course, it depends on where you're going and for how long and what kinds of things you like to do and see. For me, getting the museum card and buying strippenkaart transport tickets, which are also good in many other Dutch cities, (or the new chip card) would be the way to go. If i was only going to be in Amsterdam and only for a few days, i'd assess what i *realistically* thought i'd be able to see and add up the costs of the entry fees. Chances are I wouldn't see enough to make the cost worth it, even if it does give me access to the "fast lane" and avoid the queues in the ticket lines. If you go early enough to the really popular places, you can usually avoid the worst of the lines. Another way to avoid those lines is buy the tickets online, quite often at a bit of a discount. For our first trip to Amsterdam, Because the Rembrandthuis was closed, we didn't get the card and we never did get to some of the other attractions on our list. We only ended up going to the Rijkesmuseum that needed paying an entrance fee and also to the open air museum in Arnhem. The museum card would have cost twice what those entrance fees did. You have to make your list, check the cost of individual entry fees, and make your decision. It's sometimes a crap shoot if you don't get to all the places you plan to.