Loved the MkIII, shoot on Sony VG10 and this is certainly comparable albeit completely different with some quirks! Biggest is the issues around shooting flat. D800 is also nice to shoot on and it is certainly comparable to a 5D.
I have come around to being a Canon fan. They are so straightforward - everything is where I want it, quality is always good and if you know what you're doing, they can be blown up to a full screen.
Not a fan of the BMCC. Inorganic picture, banding, batteries, constantly having to churn through SSD cards, weight, post production lack of speediness, can't see the screen in sunlight and did I mention those bl@@dy batteries. Not my thing.
Want to go bigger and better now so am fantasizing about a C100 with Atmos Ninja or maybe a used FS100 or AF101. Don't really have the post-processing power for RAW.