So the PS3 Slim will lack the ability to install an alternate operating system.
Such a move from a rational company (not to say that Sony's rational) would indicate that they are taking a loss on each system sold and do not want to sell PS3s to the cluster-computing market, since that market doesn't buy their highly profitable games to recoup their losses.
It makes sense for Sony to try to deny the world cheap DIY cluster computing and make money selling the Cell to dedicated system builders. But then again, this is the company that broke compact discs trying to copy-protect them, so who knows.
I figure that there will be a firmware workaround available soon after the slim is released anyway.