Hey, I don't mind. There are few things more calming than some good ranty catharsis and if I went through, I would be equally, if not more ranty.
Four out of 2000...holy hell.
That is one of the reasons why I am glad that I ahven't really been rushing to get published. I know I don't want to make simple mistakes my first time in.
As for the 50% rule, I think they do something similar with the big presses. For instance, if the title sucks (left hand pile); if the title is good, but the first line sucks (left hand pile); if the title and first line are good, but you can't maintain the reader's attention for the first half of the first page (left hand pile). Personally, I think that is far. I mean, if you really want to make it and get paid lotsa money and live off of writing, you should be able to put forth the effort to make sure that you maintain the audiences attentiont he whole way through (besides, if you bore yourself while reading, it most definitely isn't good xD).
I am writing a script myself, but I am letting it evolve and become its own beast (and I most certainly won't turn in a first, secon, third or fourth draft) before I persue any sort of contest/sale.