Adam,

it appears to me like you haven't used an N810. I think you should be made aware that Maemo 4 and Maemo 5 are very different in not only looks, application libraries, and software availability but also in features and hardware resources. The N810 pros and cons list are completely different from the N900s.

The N810 is a very good ebook reader and web browser and communication device, but it's also a very different ebook reader and web browser and communication device compared to the N900. You'd not transfer your books and contacts and documents any much easier to this device than to a competing device. I don't see how'd you use the N810 as a backup to the N900. Truth be told, it'd be better to consider it a companion to the N900. And as that, it's not that brilliant.