I own the 5D Mark II and I love it, especially since Canon recently released the firmware to enable ISO, Aperature and Shutter Speed control in video mode. I work on indie film and professional video and I can tell you that even though this isn't a "video" camera, the full-frame sensor and the Canon line of lenses, especially the high-end primes, are a wonderful combination. Such shallow depth of field, such great color reproduction, and great low light sensitivity.
Most prosumer / consumer HD cameras can't touch the sensor and lens combo that this camera does, unless you get above 10K$ for your camera. Naturally, in indie film we want to get the best bang for the money, so this camera has been a godsend. A lot of companies like Redrock and Zacuto are now selling full rail systems with matte boxes and follow focus equipment for this and other DSLR's enabling a DP to utilize a DSLR like a traditional video or film motion picture camera.
One of the biggest issues with this third-party firmware is it has to be reinstalled every time you power down and power up the camera. I hope Canon sees what the community is doing and adds these features directly or at least supports the development of 3rd party firmware. We're still missing 24/25P, and a real Zebra function would be incredible.
If A = B and B = C, then A = C, except where void or prohibited by law. -- Roy Santoro