a fashion shooter

1Ds3’s viewfinder is larger and brighter (in and out of focus “snap” seems about the same as 5D with the Ee-S Super Precision Focusing Screen in it)  

Weight feels very similar to 5d with two batteries in grip 

1Ds3 files show quite a bit more detail in studio with strobes, but on a tripod with daylight, the resolution differences between these cameras are just about non existent (using the 50mm 1.4 lens at f8. (sample images to come…) 

Highlight recovery with Highlight Tone Prio – the 1Ds3 wins NO CONTEST! (see first 3 images below) 
As blown highlights is the Achilles heel of the 5D in my opinion, I think the benefit of Highlight Priority and the step up to the 1Ds3 chip is huge, coming from a 5D. 
(I know people have said that the Highlight Prio. only benefits jpeg shooters, but my experience and the below files converted from RAW show that whatever the reason, the 1Ds3 is producing files quite a bit better than my 5D does) Maybe it’s the Highlight Priority mode, maybe it’s the new chip… 
All I know is the 1Ds3 gives me MUCH better files in terms of the highlights (RAW and jpeg) with zero added work in post production. 
If this camera saves even a handful of back lighted shots for me due to the better highlight retention, then it is easily worth the investment. 

Tethering: I was able to tether to a Mac mini, Powerbook Pro, and a Dell Windows machine without a hitch. Tethering speed was very fast (seemed as fast to transfer files as the 5D is, but I didn’t time it.) 

(Apparently some photographers have tested the 1Ds3 with Highlight Priority On vs. Off. I have not done such a test here – what I am comparing is two entirely different cameras. And thus far, one camera (the 1Ds3) produces files which are significantly better than the other camera (5D) in certain areas.) My experience seem to show that either HTP works, or the 1Ds3 has better DR, or both. More to come…