Thanks, for the opinions coming in. I've certainly been leaning toward the 5D MkIII and do have one on pre-order but I saw a couple of 1Ds Mk III available so I thought I'd ask.
As far as older technology I'm a little bit jaded here since I develop IC's for a living. A lot of time the progress in technology is really no more than the same features for less money. (which is why it great) but not necessarily more performance when measured on an absolute scale. I mean that's why you can introduce the 5D Mk III at $3500 and not the $7000 to $8000 of the 1Ds MkIII. That said I was more interested in how they stack up in absolute terms. i.e. Noise, AF, and other performance like FPS, etc.
A lot of time the newer cheaper versions also jettison feature to get the price down since it is a mid tear rather than a top of the pyramid product. The best example I know of that is the PS3. Each version is cheaper than the last but the performance of the first (with the exception of disk capacity) is still as good as the latest and a lot of features were thrown out of the newer ones to keep the cost going down.