@Drem
What exactly does the use of the Symbian operating system, or the Maemo one for that matter have to do with access to Open Street Map?
The operating system handles the low level stuff. The shiny stuff is handled by the UI and in neither the Linux or Symbian worlds is this handled by the O/S.
It seems to me that what you would really like is for someone to build an application that runs on the Symbian O/S, using the Nokia Series 60 UI and provides access to Open Street Map.
By the same logic I'd be put off by a Maemo-based phone as you can't buy the Garmin satnav software for that platform, something you can do for Symbian/S60 phones.