Very interesting read. Some remarks from a Swedish perspective: at the Nobel Museum (my main place of work), we have offered audio guides both for free and for a fee (20 SEK, appr. 3 USD). The audio guides are just as popular when the visitors have to pay extra. I believe they value the "enhanced experience". Audio guides & apps are still not considered part of the basic offer in the public mind. That might change, of course, and then I assume the willingness to pay for apps etc might decrease.
I do think that for most museums, the primary target group of apps will be the visitors at the physical museum, to offer an enhanced experience or make it possible to prolong the visit by adding a virtual part after the physical visit. Stand-alone apps might work for art museums, displaying artworks (and here the iPad/tablet versions will dominate, because of the user experience), but for cultural history museums the interest just isn't large enough.
Right now I'm coordinating a mobile strategy for the National Maritime Museums in Sweden, and right now (although we're just at the earliest stages of discussions) my feeling is that we will focus on mobile web rather than apps, since it might be hard to get people to use the app "stand-alone", not connected to the museum visit. A steadily rising proportion of our web visitors arrive via mobile and those visitors will probably be more plentiful than possible app users.
thanks for a nice post and interesting comments as well!
best regards, Aron Ambrosiani web project manager, Swedish National Maritime Museums