Well.....here is another few cents and a different point of view. First there are arguments about comparisons to windows and versions of XP vs the move to Vista etc. But we are talking about a device...not the purchase of software. If i buy a PC i expect it to run a new OS released or 12 months aftter i bought the computer. However i may not get the software free.....but I do believe my device should be capable of running the software and if i choose to run the software i expect that support should be available.

Now for Nokia and the n900.
Simply put, whatever policy Nokia adopts must be profitable. When people buy a device, support is factored into the price. The support bundied into the price is for one (1) os. For handling new OS versions, there are 3 possibilities.

1. Leave the original OS as the supported version. If you want support, go back to the original version. This doesn't stop the new version being available....just not supported.

2. Make the new version the only supported version. If you want support you must upgrade to the new version first. This is a problem if some people could have a reason to resist the move.

3. Charge those who do move to the supported new version in order to recover the additional costs of supporting a fragmented user base.

Really....they are the only 3 options from an economic perspective. Nokia have traditionally chosen option #1, and for phones and even smart phones, it makes sense. Patches are treated as option #2.
However for a major release with the n900, i suggest they should offer #3. A supported upgrade attracting a price in an open source world still allows those not seeking any support to get the upgrade for free. So free if no support is needed, but for those who wish to get any support a fee.