I presume your HD format is interlaced (like 1080i)? That works.
Simultaneous viewing of progressive HD and down converted interlaced SD (NTSC or PAL) does not work on any Blackmagic or AJA product that I have seen, while the MXO may.
That being said, I love being able to output SDI, component and composite all at the same time with my Multibridge Extreme. Not to mention that the Multibridge has inputs- the MXO does not.
Chris Paul
POV