Marko Ahtisaari, Nokia's director of design strategy, sometimes begins the day by diving into a Finnish lake still partly covered in ice. He calls that a disruptive experience, and it's a metaphor for what Nokia is trying to do in the consumer electronics business. On April 25, Nokia introduced new versions of its N series handsets, which mark the company's latest encroachment onto turf now occupied by outfits such as Sony, Canon and Apple.