full read here:
a video presentation of UEFI booting (ironically in WMV format):
my opinion is that such a firmware setup may greatly reduce the choices for home users to purchase some new system and essentially limit their freedom if they are already using one of such due to certain circumstances. also software updates in signed boot managers might get prevented as well and therefore a firmware update will be required. but i do think that UEFI is a great peace of technology and that BIOS should be eventually replaced - sooner or later.
looks like microsoft responded to the issue, but apparently they do not provide enough evidence to contradict the available facts for the consequences of setting up a secure boot interface: