For the last 6 years I have been shooting with a Canon 1DS Mark II body. My plan when I bought it was to use it for 5 years and then upgrade to a newer model once they advanced 2 generations past the 1DS Mark II. Well, so far, Canon has not announced a new pro body with some of the new features that I would like to have at this point, except for the 1DS Mark III. The 1DS Mark III however is now more than 4 years old and has a relatively high noise image processor compared to some of the newer generation DSLR cameras that have come out since its release in 2007. Plus it is only 1 generation newer than the 1DS Mark II body I have now. So it would make no sense to buy a 1DS Mark III at this point given its age and the high price it is still demanding, even though Canon has not kept up the pace of releasing new Pro bodies at the same rate they did before. And since I didn't want to keep waiting for a new Pro body to come out from Canon (not knowing how long that would be), I decided to take a step backward to take a step forward. The recently announced 1D-X they are planning to release is a low megapixel body geared towards sports and news shooters, which is not suitable for me. So in the end I bought a 5D Mark II rather than keep waiting. At first I thought I might be really disappointed with it, but actually I am not disappointed with it at all. In fact, I am finding I like it in many ways better than the 1DS series body I was shooting with before. Some of the advantages of the 5D Mark II I have discovered are:
1 - Lighter weight (even with the extra BG-E6 battery grip attached to it that I put on)
2 - Bigger preview screen
3 - Much lower noise
4 - Much easier menu navigating through settings and when viewing pictures. No longer need to press 2 buttons for every function, file deletion, or setting change.
5 - Much smaller and lighter battery, smaller battery charger (easier to transport), and yet capable of capturing the same number of pictures on a single charge as the 1DS models.
6 - More megapixels

The things I thought would bother me about the 5D Mark II are the fact I was going from 45 focusing points on my 1DS down to just 9 on the 5D. But honestly it is not as big of a deal as I thought it would be. Also, people complained about the auto focus system on the 5D Mark II being slow and inaccurate. Personally, I don't have any problems with it. Focus is fast and concise so far.
The other main thing was not having the double memory card slot for the instant backup in case one of your memory cards fails. What I decided to do to reduce the risk though is to just use smaller memory cards instead. This way if a card gets damaged, the risk of losing pictures is reduced with less pictures stored on each card to begin with.
People talk about the lesser quality build on Prosumer bodies versus Pro bodies in general, but to be honest in last 6 years I never dropped my camera once or shot in the rain with it anyway. So why do I have to care so much about the toughness of the build of the body and the waterproof seals? The truth is I don't. And with the 5D being less than 1/3 the price of a 1DS body, I can buy three of the 5D bodies before I would pay for one of the 1DS bodies. So if I do drop it and it breaks, I can still afford to buy another one by not having bought another 1DS series body at more than 3 times the price.
I did a lot of shooting with the 5D Mark II the last few days and I found it a pleasure. I think maybe I am hooked now on the 5D even though it was only intended to be an interim body while awaiting the next 1DS high megapixel release. I am starting to think that when Canon eventually releases a new 1DS body with more megapixels, and less noise at high ISO settings, that I might not even bother spending the extra money for it. It hardly makes sense to me at this point and the 5D Mark II has turned out to be a great camera in many ways. Above my expectations in fact.
I would have never thought I would have liked going from a pro body down to a lesser build body so much, or I would have bought one long ago.
