I recommend people read the ArsTechnica review of Mavericks by John Siracusa, the best and most detailed you can find, there is lots to learn.
The Time Machine animation was removed because it causes the cpu to wake up (to draw the animation). Mavericks does everything it can to make the cpu 'sleep' as much as possible, which is why you get the great battery life.
It was a good review, missing major parts about OpenGL, OpenCL performance, and features for Professional users.
Also there's more than just MacBooks from Apple, and that little spinning icon is negligible at best for CPU usage, and will not do much to the CPU.
IF, and that's a big if, that it somehow was the cause everyone's battery issues, they can just put code into Mavericks to make it give us full features for desktop users.
App Nap, and Timer Coalescence has caused quite a few problems for Professional Apps. Hell Until you turn off App Nap it'll constantly Kill FCP X's back ground rendering, and cause errors, garbled sound, and video when you're transcoding, rendering, and exporting in FCPX, Screenflow, Premiere and others.
Why? Simply because once you start the process you let the machine get on with it, as doing other things can slow it all down. Mavericks then decides to F' it all up with App Nap, and Timer Coalescence.
At least App Nap can be turned off.
This is not true. The actual backup doesn't need to update the screen. Drawing the animation does.
It's not a bug, it's by design.
Whether it's on the screen or not, the CPU is still being used...