You probably know about the various race predictor charts. For example, Jack Daniels has the whole VDOT tables which you can find here. And another one that I like is the calculator from Greg McMillan's site. Galloway has one that's less ambitious (that's soooo Galloway ;) ).
So how good are they to predict your times? If they are off, do you believe that if you were in top shape, they would hold true?
And, if you're wondering, I ran 4 miles this morning.
Shake it like a salt shaker.