Well these are the things that nokia needs to improve for the developers...
1.The documentation of S60 for from 6.1 sdk to till now is full of flaws and missing stuffs..please remove the stuffs which is not relevant to public.
2.It will be better if developers get some insight in low level stuffs of symbian which is no where there to learn for public developers on symbian example: device drivers. fsy etc..
Nokia with public sdk is much of UI and engines stuff nothing much on the core level of platforms for public developers...