I've been using the 5d2 as my primary body for the past 6 month or so, and I thought it was about time to give you an update. Some of this will be obvious or a rehash of things people have said in early reviews, but I think it's still relevant as an actual photographer actually using the thing instead of a lot of photos of charts and graphs. Please keep in mind that my conclusions are based on my shooting style, which is mostly environmental portraits. I also use mostly high-end primes too, so lenses are not the limiting factor in most of my work. Ok, first the stuff I like.
The resolution is great. Very similar to the 1Ds3 which I had last year. Which makes sense as they're the same resolution and it's probably just a newer revision of the sensor. Sometimes I look at the 100% images and think that they don't look 'quite' as good as the 1Ds, but I think that might just be in my head. I haven't yet tried getting a really big print, like 30x45" to see how it holds up. My guess is, pretty well.
Colors are fantastic most of the time, as long as you get the WB right. Auto WB still sucks much of the time as it has for Canon cameras for years. It's weird, some of the time it's right on and other times it leaves you shaking your head.
Noise is reduced from the old 5D, though that camera was no slouch in noise either. I find myself comfortably using 1600 and 3200 iso with the new camera, where I'd usually try to top out at 800 on the old one. The thing is that which 6400 and up are usable, that's really only true when you've got enough light. And when you don't have enough light is when you usually move to a higher iso. I love all the noise tests and advertising images (like that motorcycle shot Nikon used to sell the D3) which show these high-iso images looking great. Well sure they're going to look great when you shot them outside in the middle of the day. Go shoot at 12k in a dark bar with a wide open prime and then come back to me. Perhaps it's really useful for sports guys who need crazy shutter speeds in middling light.
Ok, then there are the negatives, beginning with the screen. The resolution is great and colors are good and the new menu system is a big step up, but the brightness levels are killing me. The new camera's got a light sensor, so you can set brightness to auto and it's supposed to turn it up when it's bright and down with it's dark, so that you can get a good approximation of the photo you just took. No matter what auto settings I use, or the manual ones for that matter, I can never get it right. Most of the time it's too bright and my images look somewhat blown out on the screen when they're perfectly fine. I'd say it's usually a stop too bright, but if I manually set it lower, then half the time it's way too dark. I've been checking my histogram as my safety blanket, but I'd rather just be able to trust the damn screen. I never had that problem with the old 5D. Maybe there's a trick I'm unaware of.
The brightness problem is only compounded by the fact that I find the auto-exposure very inconsistent, especially when you're using E-TTL flashes. I haven't found the reason for this either but there are times when it's so annoying I just go 100% manual to at least give me some stability.
Tests have shown that the dynamic range of the sensor is a bit better than the original 5D, but I don't feel that it is. There have been a few times where I felt that my old camera would have done a better job, but I can't measure that, or at least not easily. In the past week I've been playing with the "Highlight Tone Priority" setting and been quite impressed. It very much helps the dynamic range and highlight problem, you can pull back highlights in RAW that were "No way in Hell" before, but does result in more noise in the shadows and even in the mid-tones. Especially for a photographer like me who does a lot of post processing. There is definitely more noise. Whether or not that's a problem is a picture by picture question. Certainly a good tool though, I'm going to leave it on most of the time now.
Then the silly things. A camera at this level should have a 100% viewfinder. Sony's camera has one, and it's the one big thing I miss from the 1Ds3. That's not true, I also liked not having a mode wheel that gets easily knocked into the wrong position when you let the camera dangle around your neck while you fix a light. Also, there should be more control over bracketing. The 1D and Nikon's high-end bodies can do 3, 5, or 7 images over a +-4 stop range. This is an easy thing to fix in software and would make the body fantastic for HDR work, especially landscape use which is one of this cameras fortes anyway. Oh and sometimes the camera locks up on me. Not all the time, but I'll be shooting shooting shooting and then all of a sudden the lens stops autofocusing. Cycling the power quick has always worked, but it's still disconcerting.
Though it's got obvious strengths over the old 5D, for some reason it's not nearly as satisfying a picture making tool to me. Don't get me wrong, I'm not going back as the resolution alone will keep me here, but the old camera had a rock solid feel to it. I trusted it more than I do the new camera. The 5D felt like an old friend that never let me down. Now, I always feel like I'm second guessing things with the Mark II and often I find that it was for good reason. I'm not sure if I've got a bad copy, or if the stuff that bothers me will get fixed in a software update or even if anyone else is seeing the same things I have. The one thing I'm certain of though, is that there are readers who will disagree with me on some or most of this.