Recently, Apple seems big on iteration and small on innovation. Miniaturising an existing product is definitely a good iteration, but when I see Microsoft experimenting with touch covers and the like, I do wish Apple would try one or two new things again.
That said, calling it revolutionary seems a bit much - the form factor is certainly new and unique, but none of its components (or its roles) are distinct from that of the previous Mac Pros. Certainly not on the scale of differences between the original iPad and its competitors at the time, or the iPhone, or the iPod.
It could safely be argued as a simple iteration on the PC's form factor.