The n900 has different HW as soon as it gets unboxed, pocketted, slided open, typed on, plugged and unplugged M-usb, dropped and scratched. I perdonally doubt that there are different versions, perhaps they adjusted the machines to give make 1 solding part more solid, though that is debatable as well..

Indeed don't get me started on the software part, if you read TMO once a while you can suggest there are millions of versions, you know what I mean.