N900 is a great platform, free as everyone is asking. The point is that is not for US because of the subsiding US people is looking to have.
700$ is the same price of an iPhone, the two are on the same league (more or less depending on the feature) but it seems that the marketing of 199$ + n hundreds $ in 2 years contract wins.
The only reason I can imagine (not being in US) for this being reasonable is that there is no reasonable dataplan without phone "embedded in".
S60 is OK from the user point of view (barring the UI from 1990), phones are cheap given the features, but programming for it is a nightmare...