One reason for buying a device which is linux based is precisely to avoid the problems of vendor obsolescence. For example, Sony dumped the clie line of palm compatibles, causing the more specialist software to dry up, and Sony also closed down various support and developer sites.

At least with the linux based devices like the Zauruses and Nokias it is possible to keep it up to date yourself (at least where the applications don't need a specific bit of hardware). For example, there are still people running antique Zaurus 5xxx devices with cutting edge distros like Angstrom.

Now, that's not to say I think Nokia are particularly good at supporting devices which aren't current - they are driven far too much by marketing and sales and seem to think that they sell appliances whose purpose is frozen at the point of sale, not computers whose use grows with their customers, and therefore Nokia have tended to fix and enhance only devices which are currently in the retail channel, rather than legacy products.

So, I'd rather have an obsolete Linux device (zaurus, nokia etc) than an obsolete windows mobile device!