Been running the group finder pretty frequently the last two weeks (guessing in the range of at least 20 runs), gearing up a new alt. I would say the vast majority of runs have been good to great, and not once have I seen any name calling or yelling.
I've been leveling a healing Op in the groupfinder and this has been largely my experience. After dozens of runs, my ignore list has only three names - one ragequitter and two griefers. I won't ignore someone for being undergeared, inexperienced or even incompetent. All those things can be fixed.