I always thought that humans would be greatly improved by crossing them with Kangaroos. Our marsupial friends are already bipedal and complete with little hands, so the transition wouldn't be too alien and we'd still be able to carry out most of the manual tasks we currently engage in.
Their form would provide us with a built-in pocket and a handy tail to take the strain off our feet when they're no seats left in the pub. The increased speed and endurance that would come with Kangaroo style hopping is just what we need to put a halt to our ever-increasing reliance on environmentally unsound vehicular transport.
It would also do wonders for the sport of boxing.