I tried the search, but to no avail. Is there really a need for the 3 if you own a 2? Please don't reply with "if you need it you will know"

Depends on what you are shooting really. If its people and primarily subjects that use wider apertures than you will see a small increase in picture quality. If you shoot landscapes or anything you like to stop down for, forget it. The Mk2 is the better choice. This is just picture quality mind you. The Mk3 has a nicer screen, viewfinder, menu system, battery etc

I think in light of the 5d2 pricing structure you are better off with the MK2 and perhaps pick up a 5d2 when you need the little bit extra.

I have owned all three of the DS series bodies. Currently I have both of the 3 series bodies. I use the bodies as tools to make a living & upgrade from a business perspective. My 1DS2 had plenty left in it & produced fabulous images.
However, by selling it I write off the loss & buying the new body gives me new numbers to depreciate. So while the cost of the new body may seem a lot, by the time these other factors are taken into account it works out to be cost effective.
As a picture making tool, the 1DS3 is far & away the best camera I have used. Here is a corporate headshot from a couple of days ago.

Studio58 wrote:
I have owned all three of the DS series bodies. Currently I have both of the 3 series bodies. I use the bodies as tools to make a living & upgrade from a business perspective. My 1DS2 had plenty left in it & produced fabulous images.
However, by selling it I write off the loss & buying the new body gives me new numbers to depreciate. So while the cost of the new body may seem a lot, by the time these other factors are taken into account it works out to be cost effective.
As a picture making tool, the 1DS3 is far & away the best camera I have used. Here is a corporate headshot from a couple of days ago.


That is the best, and most logical, explanation I have ever heard.

As someone who can't write off equipment, it clearly "costs" me more. I can't say that the 1Ds2 held me back, but I do like the lower noise and FAR better low light AF (I shoot almost exclusively people indoors, under bad light). It has increased my keeper rate, and made the ISO 1600 / 3200 images look better. So if you have the money, by all means, it's a nice upgrade. But if you are expecting the same jump as the 1Ds -> 1Ds2, you will likely be disappointed.

I will add something from a sport/motorsport perspective. I found the 1Ds2's buffer was far too small and writing to card was also too slow to be used for motorsport. You could say this forces you to be more selective in your shots, which in a manner of speaking is true, but say a car spins coming out of a corner, click click click, got it, but then the car following also spins, I am like, damn, lockout!! The 1Ds3 is the first full frame body that I feel I can use for sport and motorsport. The buffer is bigger and the write speed is very fast, so those 2 factors, for me, make it much much better than a 1Ds2.

Studio58 wrote:
I have owned all three of the DS series bodies. Currently I have both of the 3 series bodies. I use the bodies as tools to make a living & upgrade from a business perspective. My 1DS2 had plenty left in it & produced fabulous images.
However, by selling it I write off the loss & buying the new body gives me new numbers to depreciate. So while the cost of the new body may seem a lot, by the time these other factors are taken into account it works out to be cost effective.
As a picture making tool, the 1DS3 is far & away the best camera I have used. Here is a corporate headshot from a couple of days ago.