Think of the RED as a manual focus DSLR that shoots 12bit RAW movies at up to 30fps and 4096x2304. There is no mirror, hence either a high resolution EVF or LCD panel are used for monitoring. The RAW files are similar to what you're used to with stills, but they're nicely compressed so you can record about 4.5mins on an 8GB CF card. You can record a few hours on a hard drive.
The major difference of the 5D2 is that the video recorded is highly compressed, 8bit, processed video, similar to how a DSLR records a JPEG instead of a RAW. However, because of how the video works on the 5D2, it must downsample from the full sensor down to a 1920x1080 for the recording. If that were done with finesse, then the recorded image would be very nice indeed (save for the strong compression), but tests show that the downsample is crude, and, indeed, it looks like for every 3 rows on the sensor, 2 are not read. This is obviously not optimal. Advantages are the simplicity of the camera, and if you have lots of Canon glass you're ready to go out of the box. It really all depends on how it's image quality and robustness of the compression to suit post colouring needs holds up to your needs and expectations.
Without fully knowing your skills, background and needs, it's hard to recommend a RED. It's a unique camera for sure, and I get the feeling that one of the forthcoming Scarlet models may be more to your liking. I'm happy to answer any questions on the RED products if you need more info.