At least in Kenya, the 523x series retails unlocked for more like $200. I am only pointing this out because in your comments regarding the N96 you give both the Western price, but also the local-purchase price.

For in-country organizations attempting to use these phones, Kenyan availability is very low. In fact, the only phones listed here that you can purchase are also your lowest scorers: the Nokias minus the N900.

This is a good article doing a roundup of phones that people can bring with them to do development work, but it also highlights the differences people will face when it comes to obtaining resources once in country. An article also on in-country available resources would be great!

Also, what is the comparison of the N900 battery life when in use compared to say a 3-cell Netbook battery (smallest, most common) and then a 6-cell battery? Because for field work, that is the common limiting factor amongst all devices.