is there a changelog for BBB-eMMC flasher images? validation suite?

after downloading and reflashing with
BBB-eMMC-flasher-2013.05.27.img.xz yesterday, i see there's an even
newer (05.28) image this morning. so what does it represent? it would
be convenient to know the difference so i could decide if i cared
enough about it to download the newer image.

  also, is there a validation suite somewhere one could use to check
the functionality of any new image? just a bullet list of checks would
be fine to see if anything's been fixed/regressed.