Likewise, typing in "Next Friday" should normally mean the Friday of next week (ie, not this Friday, but the next Friday). Right now, it does the same thing as just typing in "Friday" so there's really no point.
Just to be clear with an example: Today is Wednesday, November 21. If I type in "Friday" the date field should be 11/23/07. If I type in "next Friday" it should be 11/30/07. Right now, both phrases result in the same date, which doesn't make as much sense.
I could see how things like "Next Monday" might get confusing, since they span different weeks by most people's calendars (ie, in the above example many people would consider 11/26/07 to be "next Monday" regardless), but I'm still inclined to think that "next" should always mean "the one after the coming one" since it's fairly rare in a GTD system to enter dates in the past :)