There is a few X3i's on eBay for $195 last I checked.

I know there is Abiword on the N800 and I believe that opens .doc documents.

You'll find the N800's screen to be simply amazing compared to pocket pc's, but the software is a little immature. Though I expect the next 6 months to be a good time for the little tablet, as Nokia claims they are going to give it a good push.

Considering you keep your devices around for years, a linux device such as this should provide a good platform to grow with.