I think another thing that can contribute to streaky windshields is a pitted windshield (like mine - looks like it is covered with pollen when looked at from an angle) that collects road grim and oil from the road during routine driving. I periodically wash it down with isopropanol and then wipe the blade. I think the mono wiper is better than the standard type because for a brief instant during rain a standard passenger side wiper throws a huge amount of water right in your line of sight before the other wiper can clear it off.
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (194,000)
1999 E300 Turbodiesel (244,000 miles, dies at 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles)
2011 Audi A4 Avant (129,000 miles) hate this car!
BMW 330 xi 6 speed manual (100,034 miles)