Curmudgeon's comments seem to me to point in a valid, direction. What area of your windshiled do you use most often? Yes, yes, "all of it", but consider the problem from an ergonomic point of view. My car's defroster is underpowered, and I know what area of the windshield needs to be clean (I don't want to spend any more time outside than I have to scraping it!). For other things, I can use the side windows.
Likewise, in the rain, there are parts of the windshield that you don't really need to have clear, or that you could do without if certain other parts could be kept clear faster or better. Granted, it's probably the middle of the windshield that needs the most work, but if Nokia really wants to arrive at a "better" system, he might try approaching the problem of the driver's needs, rather than straight mechanical engineering.