The Apple Mac Pro remains the most robust platform for photographers, including the best value by far: the Apple refurbished 2.8 GHz quad-core Mac Pro for $1819.
Which makes one wonder about the Mac Pro radio silence: Analysis of the new Mac Pro — Oops Nothing Announced.
While the new iMac is increasingly attractive, the fact remains that it can become a tangle of cables when one wants to add performance and backup. And no PCIe cards. And big downtime if an internal drive or the screen fails. The Mac Pro sidesteps those issues and while the iMac CPU beats the quad-core Mac Pro, this is only one performance factor to consider.