It's constantly jumping between 10% to a whoping 60% (25% seems to be the most normal peak point, but I have seen it jump as high as 60%)
Here's a screenshot so you can see I'm not just going crazy (no games or Action! compatible apps are running)
Action! version is 1.25.3.
CPU: i5-3570
GPU: R9 280X
RAM: Corsair XMS3 12GB
OS: Win8.1 Pro 64bit