Sigma lenses are something like the physical properties of the Pentax K mount, but only 44.0mm flange distance (same as EF-lenses), and autofocus-routines are identical to the EF-specifications.
So, you can mount a Pentax K lens and use it in full manual (and even focus 'past' infinity).
Or you can take an EF-lens, rip the mount and electronic contacts off, replace it with a K-mount and whatever electronic pins you need, then you can use it on a Sigma Camera (and not on your EOS camera anymore).
Pricing it a bit more in the realms of reality may have something to do with the 0 they've sold so far, maybe because the boss carked it, or maybe from the D800 being less than half the price. Still, take it to $1000-1500 and i'll start being interested...
I liked the re-launching of the OM-system, but too bad it's just another EVIL 4/3rds camera, still a 2.0x crop factor. (Will olympus ever ditch the 4/3rds and go back to FF or aps-c? I doubt it).
And nice that there's finally some fast lenses for m4/3, but don't forget that 17.5mm f/0.95 is just a FF-equivalent of 35mm f/1.9, so it's not too impressive (but it's a start)