if you want the n900 to be wifi only, take the sim card out
With free WIFI becoming so ubiquitous (McDonald's chains, Starbucks chains, free WIFI at hotels, public WIFI's, at home, etc.)
I'm just not seeing the case for embedding so many devices with power-sucking, surreptitiously running and space-hogging cellular radios in devices that were never intended to be cell phones.
The Nokia 770, N800, N810 and (arguably) the N810WE were all GREAT with just WIFI for connectivity.
Considering how well that's worked out, and the move of Apple to provide non-cellular versions of devices (iPhone->iPod Touch, iPad G3->iPad Wifi). Google has changed the specs for Android so that it would run and make sense on non-cellular devices, recognizing that people might prefer a good embedded OS on a non-cellular device. Even Barnes and Nobles has decided to release a wifi-only version of their Nook eBook reader, very recently.
With the sneaky use of the N900's phone-home registration as an example
the unnecessarily short battery life
added heft and smaller screen