iPhone / iPad multitasking
We don’t give the idea of single-tasking enough credit.
When I develop an iPad or iPhone application I get to control the entire experience the users having. The whole thing! There aren’t any other windows demanding attention, there aren’t interruptions (aside from alerts, which is why I think apple was reluctant to offer them to developers), the only App I have to worry about noise from is the iPod app and I can turn that off, there aren’t system controls distracting the user, at the user level my application is the device!
What’s not there gives the designer / developer incredible power to define an experience.