The camera looks great, however the MPEG II recording codec is still 8-bit which isn't a professional bit rate. It leaves you without any latitude to color correct, a big problem for Canon 5D Mark II users. The good news is that there's an HD-SDI output which will allow you to use a third party 10 or 12-bit recorder.
About the hype that this is a Red Epic or Arri Alexa killer, it isn't. I own the Alexa-Plus and Arriraw, or it's 12-bit 4:4:4 capability, coupled with the camera's 14 stops of latitude ends that argument. The 300 competes more with Red's Scarlet, however at twice the price it may, or may not.
I would love to have the 300 as a second unit camera so I could use my EF lenses, including the 14mm 2.8, 20-35mm, 14mm TS, 85mm 1.2, 135mm 2.0, 400mm 2.8.
Too bad they make you choose between EF and PL mount models because I'd like to be able to use my Master Primes, too.