Kristine's hack will set you back a few (Star)bucks, but may be worth it:
When our son started eating solids, the poop — and therefore the diaper pail — got a lot stinkier. A friend suggested that I dump a bag of whole bean coffee in the bottom of the pail before I put the bag in. In order to contain the beans, I put them in a zip-up mesh laundry bag. I couldn't believe that it worked! At first it smelled a little bit like Starbucks in my son's room, but after about a week, we really couldn't smell the coffee, and even better, we couldn't smell the poop either.