Unbound is a Photo Management and Viewing app for iOS with separate version for iPhone and iPad. Next to browsing, viewing and sharing it allows to move, delete and upload photos right within the application. The clean and simple user experience is further improved as Unbound caches photos you view from your Dropbox and hence reduced load times as you show around the latest picture of your kids.
I am using Unbound for a couple days now and need to say I am very happy with it. I am staring to consider dropping iPhoto on Mac OS X as well and replace it with either Unbound for Mac, which is currently in beta, or with Pixa.