1. Apple takes 30% of the gross revenue of any app you develop. They will not allow just any app on the device.
Contrast with Nokia: build whatever you want.
2. Google has poisoned their well by unreasonably rejecting applications on their platform. Contrast with Nokia: upload whatever you want.
In addition; - Maemo is built on debian. That means you can port many already existing applications to the device. - Nokia is the #1 cell phone maker in the world with a market share in Smart Phones vastly larger than Apple and Google combined.
I think the wise developer will see that the opportunities here are huge.