Three things:
a) I have an S60 phone and I must say that if that is all Symbian can offer Symbian is already death. (have not seen N97 running). The system is unresponsive. I don't blame it. It's been a long road for symbian and it never had an older brother to help it improve multitasking like windows or linux for desktops and servers.
So that means Nokia NEEDS Maemo to run in a phone. At least one.
b) The problem is always the same. Maemo should run in two very diferent devices. One of them is a N97 sized tablet so you can carry it around with all your best software on it. If that has a phone it is ok for me (in fact I prefer that to have a phone). So RX-51 is a great step in that direction.
Then, there is another device, that can be as big as an small kindle, that connects wiressly to the phone and let you make all things you'll do with it but without taking it away from your pocket. That device don't need to have any phone capability (like N810) yet it should extensively use bluetooth to work with the phone so well you simply forget it is not a phone. A little bit like what happens with 3G Internet connection in N810. Once you paired N8X0 with a phone it actually has 3G internet built in. It becomes easy, fast, and transparent as if it had a SIM on it.
That device should have a much bigger screen, loud speakers, nice integrated keyboard, ... Much more portable than a Netbook and usable as a phone, as a PIM and as an Internet Tablet.

3) If RX-51 is going to have phone capabilities that means it is going to have a good integrated PIM. Hope they build it having very clear that that PIM should work seamesly as a SIM phone and as a virtual phone attached to your real phone using the protocols we alreardy have: bluetooth headsets, headphones, bluetooth PIM, bluetooth data, ...