Re: it's a chimney
"If the Mac Pro is meant to sit near the user, then taking thermal design (with its acoustic implications) as the starting point is very sensible. Storage and and accelerator cards (more than you could fit in an old MacPro, you could now have a little GPU render farm in a rack) can live elsewhere.
"Should the Mac Pro fail, just unplug it and plug in a spare Thunderbolt-equipped machine - storage and accelerator cards will still be available to it. Some people might not even need to bother with a new Mac Pro, and will plug in a Macbook Pro."
Thing is that you could do all this if they had kept the same case type. Plus having all the options of internal expansion for those that want this.
The point about noise makes sense, and I know there are some people who are currently lugging Mac Pros around to locations who are drooling over the new case. But I find it hard to believe that there are enough of them to make up for what is lost:
*The ability to mount 4 (or more if you use the optical bays) internal hard drives - which for many users provides more than enough storage without expensive external arrays.
*A standard size graphics card. Its hard enough to get manufacturers to make third party graphics cards when they only have to write special firmware. If they have to design a special form factor then that is going to make upgrades much less likely.
*8 RAM sockets. It looks like the machines will max out at 128GB RAM, but with only 4 sockets that means using 32GB modules. Going to be a while before you can do that for less than you paid for the machine.
*PCIe slots that don't require you to buy a Thunderbolt chassis.
Apart from portability and less noise - which are important but niche requirements - the only thing you seem to get in exchange is a cool look. Which seems an odd exchange for a Pro machine to make.
For the record I'm a long way for being in the market for a Mac Pro myself, but I do work with the hardware and users a lot - though mostly at the freelancer/micro-company level.