If a new wiper blade skips and judders across your car's windshield, give it some time---sometimes that's just the rubber being broken in. I used NWB replacements on my Jazz and I noticed on the first three weeks or so they skipped across my windshield after operating for about 20 minutes. It eventually and gradually went away.

When the wiper blades are old and you still get the judders, though, you should try cleaning the windshield itself.