Think everyone is judging really early, From the design shown though it does appear to be proprietary design for graphics processing.
There will definitely be multiple options available and I believe that this probably means that there will be a way to change it, or upgrade it in the future. Though lost is the ability to use the available PC Graphics cards.
The fact it is only 1 CPU does upset me, hopefully there will be a possible change of some sort on this in the future though. I do tend to believe the CPU will be upgradable in the future rather than soldered in.
There are legitimate concerns here, but I for one would reserve final judgement till we actually see the final product.
The one criticism I don't really get is the people panicking about if CUDA will be possible, because I am sure if enough Pros request it I am sure Apple will make sure to offer a CUDA powerhouse as a BTO Option. Just wondering on another note but aren't many CUDA accelerated applications also working on OpenCL support, I know Premiere Pro is.
I hope Apple is aggressive with this and prices it very aggressively, because honestly pros money isn't what apple will be wanting on a per product basis, but more likely their loyalty which = tons of new apple users as pros are generally the people who recommend computers to most people. The uninformed will ask people they believe know what they are talking about so the more Apple keeps happy the better.
If I am honest I am a bit skeptical at this point with this Pro, but I think it will grow on me, and hopefully be priced reasonably to the point it will make sense to buy it once I am able to save up.