That's not a valid argument for a device which is built on an operating system that has VERY broad hardware support.

They only need to maintain development for different input methods; the N810 has a hardware keyboard; presumably they have levered a keyboard controller chip/infrastructure that had support but even if not, its not like the N810 needs an entirely new OS to support it, over and above the N800.

Proof in the pudding, the OS "designed" for the N810 is running on my N800 (and on hundreds of others right now no doubt).

One of the principles behind Linux and other open Unixes is to provide support for the hardware that people have. Nokia hopefully fully recognizes - there's no reason to expect otherwise - rather than heading down the walled off garden path such as Apple travels.