In short, no. The secure boot is essentially optional from what I've seen so far; put Windows 8 on any old motherboard and it should work.
The whole reason this has come about is due to the vulnerability of people faking BIOS IDs and manufacturers on startup, allowing auto-authentication of pirate copies of Windows Vista and 7. In order for this auto-authentication to work in Windows 8 on a shipped bundle, secure boot will need to be activated. After the initial secure boot and activation, hopefully it can be turned off and allow more open access on OEM machines. (If it doesn't, then we have a problem.)
Great.. so its a good thing then, because maybe IT people will realize its not even worth pirating Windows (well, actually they won't be able to). Then they just edit the BIOS setting and install Linux.
It stops an avenue of piracy sure, it also stops code injecting into the startup which is also cool. The fun bit is going to be all the disk encryption software that will take a hit when people migrate to 8 (unless it's signed).
It's a pain agreed, but hopefully doesn't affect the ability to keep your system open enough to install non-windows OSes or restrict using non OEM equipment to run Win8.
The whole reason this has come about is due to the vulnerability of people faking BIOS IDs and manufacturers on startup, allowing auto-authentication of pirate copies of Windows Vista and 7. In order for this auto-authentication to work in Windows 8 on a shipped bundle, secure boot will need to be activated. After the initial secure boot and activation, hopefully it can be turned off and allow more open access on OEM machines. (If it doesn't, then we have a problem.)