I have a friend who submitted to most microstock site with a 5Mp compact.
He was trained in a commercial photography college in Tokyo. His works have a professional polish about them. Unfortunately he didn't pursue a career in photography after returning home.
Having said that I would consider DSLR a more productive and easier option than a compact to produce stock photos if you do high volume of shots weekly. The price of a DSLR is getting much cheaper these days.
Because of the questionable and inconsistent standards among QC inspectors, you just don't want to give them any excuse to reject your hard work.