I'm not sure that I would be looking at a WiMAX solution, even Clearwire have suggested that they will be migrating to LTE in the future, although I believe that they will run both in tandem for some time.

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.

Can it be a useful backup when used in conjunction with another device (say if N900 breaks & I temporarily need to use another phone for calling but can tether that to the N810 in the meantime)?

Right. Actually I am new to the whole Maemo/MeeGo world. The open source nature of the OS is what is luring me to it. I like the idea of the big screens that other devices have but I don't exactly want to be forced to use Android. Also, the customisability has to be nice if one knows what they're doing.

I'm coming from a bunch of BlackBerries (8100, 8320, 8310, 8900, now 9700) & a few S60 devices like the E61 & N95-3.

I'm not clear on what you mean with backup. Functionality or content, and what part of it. The N810 will work fine as a browser, it has the same Opera beta version that the N900 just got, and it has several of the other browsers that N900 can have. Both have pidgin and similar for IM, some ebook readers, music playback. Both has underwhelming navigation.

You can't have as many programs installed on the N810 as on the N900, it'll complain sooner. The same programs are often not available on both devices. The "same" programs are usually quite different in looks/menus/versions from the two devices. One of the things that struck me first with the N900 was that many programs I expected to be available, hadn't been ported from the N810. When they came, they were changed.

So, it's really not like having to computers with the same OS. It's more like Windows 95 vs Windows NT. Yes, in theory they're quite alike.