I have said before that I believe 2010 will be the year of maintenance cost for iPhone apps. The iPad is the manifestation of this. Sure, an iPhone app can run on the iPad, but you really need to create an iPad version of the app to get the most out of it.
With the App Store effectively splintered across the iPhone/iPod Touch and iPad "platforms," I’m not sure the device offers enough incentive to gamers to opt for an "iPad-enhanced" version. Chris Grant (from Joystiq)
Fragmentation is coming in the Apple camp as well, as we know it from mobile web, J2ME, Symbian and Android.
My bet is still on the Web; mobile or not.