Frameless windows and a soft top - tough to get a completely waterproof seal with that combo since the rubber weather stripping has to have some give to it. One thing I haven't tried yet is closing the passenger door with the window down, then rolling it up and comparing that to just closing the driver's door with the window up (rather tricky to roll both windows up after exiting the car).

I get just a little dribble or two on the inside of the window and, since I'm going to wipe down the inside windows when I wash the car anyway - along with the door jambs, sills, under hood and trunk - I figure it's really no big deal at all.

EDIT to add: seriously, unless the thing leaks so bad that you get wet when driving in the rain, I don't see an issue. Even in a heavy rain storm you aren't getting a pressure wash at the point where the glass and weather strip meet so there should be no leaking under those conditions. But I don't drive my car in the rain so I'll never know!