More than most people will need, but all the camera you'll ever want.
Pro level camera at, almost, consumer level prices
None that make any difference
The Bottom Line:
Great camera, well worth your time to learn to use it fully. Won't disappoint.
This will be a short review as technical specs abound online. Mostly just want to sum up my experiences with this camera.
First off let me say I've been an amateur for 30 years drifting in and out of the hobby over the years. Shot many different types of camera and finally went all digital about 5 years ago.
The 5D MkII was my first full frame, near pro level camera and after many months saving and selling my other gear I finally got one.
My best initial device. READ THE MANUAL. While this beast is easy to pick up and use, I learned to my detriment, that there are some menu settings that are best left untouched, or at least not messed with unless you have READ THE MANUAL.
I won't go into details because I honestly can't remember how I messed things up but lets just say I was getting some seriously weird things in my images.
Anyway. Its a full on camera, with all the standard modes but not some of the convenient presets that the 7D and 50D have. If you aren't sure you are up for the 5DMkII get a 7D. Its almost the same performance wise but more convenient for the causal to serious user.
That said this is a fantastic camera. Being a long time 35 mm guy I can make more sense of what to expect with lenses using a full frame camera. Since I like to shoot sunsets a lot (live on the east side of a lake facing west) the ISO range on this camera is phenomenal. I routinely shoot up to 3200 iso (it'll got to 128,000 with a custom preset, READ THE MANUAL) and see little detectable noise that is easily corrected in Lightroom. At 128,000 you can probably photography the inside of the lens cap.
Menus are easy to navigate and most of the standard options easy to find, though its starting to get close to menu overload on these cameras. You can set custom menu options for things you might tweak readily but if you are like me most of what you are likely to do will be in post processing anyway. I find messing with the camera settings too much is dangerous if you forget to change things back when you move to a different shooting situation.
Perhaps the only complaint I have is that with the battery grip fitted and two batteries this sucker is heavy. I like beefy cameras cause I have big hands but after a day of lugging this around with a 100-400 zoom on it your neck or shoulder is going to feel it. However remember this thing is pretty weather proof and if you ever get caught in the rain, or face down on the lawn trying to take macro shots when the sprinklers come on, you'll appreciate it.
Can't say I have much experience with the video capability. I'm not a video jock and I know the 5DMKII was getting rave reviews for this function but I guess its just not my bag.
The one thing I may recommend, and I don't usually, is get a third party extended warranty. Usually I don't bother but this was a relatively new, at the time, $2300 purchase and the extra $100 or so seemed worthwhile. Most extended plans include an annual cleaning and I found with this camera I needed to send it in within a couple months. I don't know what the deal was but I took it on a trip to Europe and when I got back noted that subsequent pictures had a lot of specs in them. When I say a lot I mean >50 because I had to spot correct them out in Lightroom. They showed up mostly in pics at high aperture which generally indicates they were on the sensor. I was somewhat surprised that such a supposedly weather proof camera was prone to this problem but have read elsewhere that this is a crap shoot issue on all DSLRs.
Overall I'm really pleased with this camera and would highly recommend it to anyone wanting to get into a full frame. If you are thinking of picking up an older 5D MK I, think really hard unless its good and cheap. Canon really up there game on the 5DMkII and difference between the MkI and MkII is lightyears.