Adobe flash player is not software that is implemented into a computer/operaing system, its a browser plugin. Flash player is not installed in either firefox or IE by default. If you want more information on the security of adobe flashplayer then have a look at this long list
. The iphone thing is more of an issue with apple.
The reason that all the photo's flow fluently is because they all have to be loaded up when the flash player starts. If you don't end up viewing or looking at all the images then its wasted time/bandwidth.
if a flash gallery is what you really want then by all means go ahead and implement one i'm not stopping you. All im bringing up is my opinion and the issued with it.
The way you have implemented it in your website is nice, but at the same time you also have to note that its only a small portion of your website that is using it and the amount of images you have is small and the size of them is small. BTW your photo's are awsome
a system you may also be interested in is Lightbox