It's not hard to manage one queue for multiple people... Just have each person be responsible for moving a new movie to the top of the list when they send one back. My girlfriend and I do this all the time, and we have totally different tastes in movies.
When I send a movie back, I then go make sure another one of my movies is at the top of the queue. If I send two back, I make sure two of my movies are at the top of the queue. When she sends movies back, she does the same. If we both send movies back and both perform this act, whoever does it last ends up at the top of the queue - but this doesn't matter as there is still the correct number of both my movies and her movies at the top of the queue, and all will be fine as soon as Netflix receives the mailed discs and sends new ones.
This simple act of updating the queue ensures that we always have equal numbers of DVDs either at home or on their way. Don't you have to update your queue after you send movies back anyway, to choose what you want next? Or have you organized the queue into some perfect list where you just get movie after movie without any input on your behalf?