Show CPU usage
CPU usage depends on CPU frequency. Now, most CPU have Power Management feature (Speed Step, Power Now! etc...).
I think that CPU usage is not important.
Know CPU usage important, for example, when testing software RAID or Full Disk Encryption systems (BitLocker, TrueCrypt).
For example, look at HD Tune screenshot with CPU usage info: http://www.hdtune.com/images/screenshot.png But HD Tune tests (and show CPU usage) only on disk-level tests, but file-level (used by CrystalDiskMark) are more interesting.
Sorry, I have no plan to support to show CPU usage, currently.
It'll be great, if Crystal Disk Mark will count of CPU usage during each test and show average value after each test. (I mean separate CPU usage values for each test - seq, 512, 4k - and separate for read/write)