With each new generation of graphic card, NVidia makes two version, a consumer one and a professional one. It is now true for the Fermi.
There will be three different models similarly to the three models of GeForce GTX4xx. These new cards have a few more features than the consumer ones, in particular support of EEC memory, and it doesn't limit double precision calculations, which are limited at 25% of their total capacity on the GeForce GTX.
Of Course, these graphic cards will come with specific drivers that alone justify that professionals buy them instead of the consumer GeForce.
We don't know if Apple will make those cards available for the Mac Pro, but if they don't provide them with the appropriate drivers, the cards will be just a little more powerful than a GeForce GTX, but not much, and certainly not enough to be worth 3 to 4 times the price of a GeForce.
