Have you seen the price ? The mount cost the same price as the camera.
What's interesting with the Canon EOS 5D Mark II is its affordable price, much cheaper than a Red One. If you just have the budget for the camera, you won't spend it again simply for a mount that you can easily make (adjusted to your actual needs) for less than $100.
My opinion is that this mount is just "for the show" and is overpriced compared to the camera's price (common, it's just metal bars), it shouldn't cost more than 1/10th the price of the cam.

All you would need for any camera really is a rod support, the shouldermount would be the best all around option I think, a follow focus system, and, only if you really think you need it, the mattebox. Redrockmicro seems to have the most solid accessories but these DSLR setups are way too much, especially because they take away from the cameras' ease of use with all the junk strapped to it. The same can be said of the RED Cage setup. Granted, if you are in a situation where you need a dozen accessories screwed in to the camera, then these cage setups make sense, but for most the bare essentials are more than enough, with the addition of a Noga arm or some kind of mount for an external LCD.

Most of the cost of those bundles is for the follow-focus system and matte box; if you just want the shoulder mount it's $350.

I've been playing around with mine fitted with a 24-105 IS. It is one of the single-mode stabilisers. When panning I find that I need to switch the IS off, otherwise you sometimes get jerky pans.

zacuto has been putting together some interesting dslr packages as well.

sometimes a little heft is a good thing. the glidecam smooth shooter/x10 stabilizer arm loves 10-12 lbs., and most mid to high-end tripod heads feel best with a bit more weight than the 3 lbs. a bare 5dm2 'rig' provides. and if you were to take the 5dm2 on a professional video gig, this rig would certainly help make you look more legit.

i agree one of the major strengths that the 5dm2 has over traditional video cameras is definitely it's size. throw a cheap cokin p filter ring in front of the lens, and you're basically running a scaled down version of the redrock rig.

bare camera/lens or tricked-out rig... the nice thing about what redrock and zacuto are doing is giving us some options.

canon should have added a little hinge to be able to tilt the screen. My favorite way to hold a camera for stability is like a football, but on the 5d that means the screen is under your armpit.