But it makes it harder for everybody else. For example, it is impossible to exchange the sim in case of bad reception/expired credit etc.

Oh, well, I have not been using N900 phone functionality all that much, until recently. And that just because I have got a discounted phone tariff on the sim I have in the N900.

I could as well use it with no sim at all in it, my normal usage would be practically unaffected.