In my experience, CK is at least as valuable as, say, MyFICO. The former has proven to be more sensitive to changes in my credit profile -- for better or worse -- than the latter.
Starting Score: 653 (11/1/2011 TransUnion)
Current Score: 719 (5/3/2012 TransUnion) 572 (3/21/2012 Equifax) 762 (4/14/12 VantageScore)
Goal Score: 700Take the FICO Fitness Challenge