Dan's Data letters #122 (page 2): "Can't get a 550EX? Consider a 420EX. Can't afford that? Consider a Vivitar 850AF, or Sigma EF 500 DG, or Promaster 5550DX, or something. Anything you can angle up to bounce off the ceiling (assuming the ceiling isn't 30 feet up and dark brown...) is better than on-camera flash, provided it integrates with your camera's auto-exposure, or you've got your exposure act very thoroughly together and can set things up manuall"