Well i love and hate the idea of such a magazine.

The thing i hate about it: all stuff mentioned is dedicated to the
developer scene, so why not aiming at a wider target readership
by implementing much "easier" content !?

The thing i love about it: i would read it! Because i am interested
in it. The enduser that NOKIA is targeting at certainly won`t.
But count me in as regular reader!

Ok and as another reason is, that i allready develop a monthly
ezine that you can get here: http://epo.endorphinum.de

So my tips for you would be:
Stick to the size of 800x480 so that you can distribute it to
much more people and devices!
Offer it as PDF so that if people do not want to read it on their
device, they can print it out and read it in bed.