I see why they went with the approach they did: we're past the days of optical drives, spinning platter storage, and internal expansion cards.
But the decision to move to laptop-style integrated GPUs that presumably cannot be upgraded, I'm not to sure about. While it's true that GPU performance has plateaued lately I'm not sure this makes it a good purchasing option: I expect a computer to last 5-6 years, and I'll upgrade the RAM twice, and the GPU after 3 years.
I know that the new Thunderbolt 2 connections allow for an external PCI-Express enclosure that could contain a higher-performance GPU, but PCI-Express 3.0 specifies about 1GiB/s per lane, and a GPU uses 16 lanes, so that's 16GiB/s, but TB2 only provides 20Gbps (2.5GiB/s), a fraction of PCI-Express bandwidth.
The only other option is that the GPUs in the MacPro will be user-upgradable, but given the expected tiny market it's unlikely many manufacturers would get on-board, and it being AMD means that NVidia's CUDA won't be available. Hmmm.
I might get a new Mac Pro, but I'll buy it knowing that it will likely be completely obsolete within 3 years.