Independed of whether mobile-review actually does have a N900 prototype and whatever software they might have, two things need clarification:
1) Current software, even that it is still under development, is stable to a degree to use it as the only device. I have no statistically relevant evidence except our global crash level reports from each device and my own experience using it every day already for 3 months, but mobile-review's experience cannot be based on the latest software.
2) Nokia is not going to ship the N900 with low quality. We are introducing a major milestone in the evolution of Maemo and, therefore, the quality of the experience must be the same or better than our smartphones.