What you and many others fail to see is that the N900 is not "the next model" in a series of high-end Nokia phones. It is the very first model in a series of non-phone devices that has some minimal phone functionality.

Comparing S60 to Maemo 5 would seem like - well, yes, regressions, as you said. Lots and lots of features missing.

But that's just not what it is. What you do is like comparing the very first camera-phones to a high-end professional camera of those days. Yes, there were "regressions" then compared to a real camera, but that's not what you'd call it... it was the beginning of a new functionality. That how I see telephony on Maemo devices.