I think that what Nokia needs besides good hardware (which is actually provided), and good software (seems to be working on ?), is to care about developers.

I mean, to give the same importance the "developer experience" as the "user experience".
It have to make it easier to develop or to start developing for maemo/symbian .
It have to provide tools for major platforms, good documentation and a good system for publishing/selling applications. I'd say something like the AppStore, but without all the AppStore nonsense.
If Nokia can provide an outstanding and attractive development solution, and create a good business opportunity for developers, it will rule the world .
To see what I mean, take a look at how many questions were asked on stackoverflow containing the following tag:
iphone --> 5,793
maemo --> 4
symbian--> 113

I know that StackOverFlow.com isn't the best place to compare the number of developers for these platforms, but these numbers are expressive.