Dan Frakes reviews Apple’s new pro desktop for Macworld:
Depending on your particular uses and needs, the new Mac Pro may be exactly what you want (a state-of-the-art, multi-core-processor, workstation-GPU computer that doesn’t waste space and resources on expandability you may never use), or nothing like what you need (a workhorse tower with tons of bays and slots for expansion).
For many years, “pro” meant a big, expandable tower case, lots of internal storage, replaceable graphics cards, and so on. For Apple, it now means “maximum performance when using pro apps.”
The Mac Pro is far more computer than I —and I suspect many others — will ever need.
See also: More by Frakes, wherein he posits the iMac is the “pro” desktop.