Seems faster than AME (CS6)
My initial attempt at this was disheartening, because Activity Monitor showed that compressing an HD iphone video only used 400% CPU on my six core Mac Pro (Mid-2010), so I quit and went over to Adobe Media Encoder (CS6) to do the job. My previous experience was nearly 100% usage on Compressor FCP 7 and AME CS6 applications.
I repeated this today, letting Compressor run to completion.
It completed faster than AME, even without the CPUs being totally used, Compressor requiring about 24 minutes vs 31 minutes for AME (CS6), even when using only 400% CPU.
Another rendering done today used about 900% of 12 possible threads for a 640x480 encoding.
gapbob about
Compressor