BTW... I decided not to buy this Mac Pro since I could never expand on it...
yet another mac that was made wrong by design...
Hans - that depends largely on what you need to use it for. For photography and graphics/layout/design works the Mac Pro is quite fine
even in the basic configuration. I sat in frot of one and worked in Photoshop - it´s absolutely great, like a charm.
I didn´t try APG or PTP - but there´s a lot of OpenCL developlment going on . . . which will boost it very much.
Using it with Cinemy4D and Maya as well as with MediaComposer it´s a pure joy working on it.
Of course: we as professional users need to re-think hardware-strategies. I appriciate the strategy of external components: you can use them
on different machines instead of needing to buy a card for each of them . . . . and you can use it on lacation: the Pro is so small that you can
take it to almost every location you´re shooting when you use not too big display.
You can even use the external devices on a coming generation of MacBooks.
So in the end as a producer you save a lot of money.
Doing 3D-design and 3D resp. animation work with 3D-CGI rendering i wouldn´t go for it, if there´s a demand for dedicated cards - which i didn´t
encounter so far. Also for panos over 25GPx i would prefer a PC. But i use MacPro AND PC anyway . . . .
You see: it´s ALWAYS a question of what you REALLY need . . . i would HATE working ONLY on Windows . .
An actual top-model iMac with i7, 1TB SSD, fast external HD and 32/64(?)GB RAM should do good enough for APG and PTP - and you can put it into a flat flight-case
for using it on the road. I rented such a setup some weeks ago for a people-shooting on location - it performed absolutely great with D800- and H4/40-image data in Photoshop.