Microsoft and new hardware DRM
This will not affect Apple. They have their own hardware, and OSX has never had problems supporting new or external devices. Apple can buy licenses to proprietary drivers. However this may hurt Linux, since it will run on any vanilla box out there (no specialty hardware required).
Best case scenario: this is great because it will this be a nail in the coffin for widespread Longhorn adoption. Microsoft tries to force this on the public and doesn't put support for regular monitors, sound/video cards into Longhorn. Companies like Dell may sell computers equipped with Linux to avoid higher hardware fees (associated with brand new hardware) and to avoid having to sell a new monitor with every new systems they sell. I wrote about this in my last post.
Probable scenario: I doubt this will hurt Microsoft, or do anything at all. Longhorn will probably still support regular hardware as well. Few will buy these new monitors or video/sound cards (unless forced on them by the big 5: Dell, HP, Compaq, Gateway, IBM), so they will be sent to the DRM graveyard along with ATRAC3 and so many others. This is what I expect, but I have the suspicion Microsoft knows this too, and has a plan so that their new hardware isn't created for obsolescence.
Worst case scenario: Longhorn only supports specialty hardware, widespread Longhorn adoption, public acceptance of this new hardware DRM. This would be a brick wall for Linux drivers. The new drivers for this new hardware for "security" sake will be closed source (or have the 'open' label but not really be open; i.e. see Microsoft openness on office format) and harder to hack around. Linux will be reduced to working only on new specialty (how many hardware vendors will create hardware just for linux??) or old hardware.