>This offers almost no advantage over a late model iMac with a Thunderbolt-to-PCIe breakout module (which is what many power users have been doing in the years since the last update).
A few big advantages over the iMac: Xeons processors, so more cores & more cache; ECC RAM; and (two) workstation graphics cards. Six thunderbolt ports means up to 36 (!) PCIe peripherals by daisy chaining, which means a lot more expandability than the iMac or even the 2010 Mac Pro.
I suspect that a lot of people bought the Mac Pro despite the fact that it has Xeon processors, rather than because of it. They're a lot more expensive without a huge performance benefit for desktop or workstation applications.
The main advantages of Xeon were dual-socket support and support for oodles of RAM slots, and the new Mac Pro supports neither of these things.
I think you’re omitting the Xeon’s increased stability versus consumer grade architectures. Many Mac Pros are used to run non-stop, they need to be more dependable than other computers.
Does this really matter in 2013? Serious question. I could see ECC having been useful in 2000 in the midst of the megahertz race, but I'm not too convinced about today...
The probability of a bit error on normal RAM is quite high [1]. The more RAM you add the more likely you are to see corruption. Not that ECC fixes everything - I still see uncorrected ECC errors on the older HPC nodes on our grid.
The most basic forms of segmentation aren't especially relevant to the discussion of the finer points of where Apple is targeting this machine. It would be like bringing up the high-power engine in a sports car, when the discussion is about where within the sports car market the maker is aiming. That it has a high-power engine is generally a given.
A few big advantages over the iMac: Xeons processors, so more cores & more cache; ECC RAM; and (two) workstation graphics cards. Six thunderbolt ports means up to 36 (!) PCIe peripherals by daisy chaining, which means a lot more expandability than the iMac or even the 2010 Mac Pro.