hmmmm, I'm using hitslink as well. in the beginning I was watching very closely and the stats matched. But, since you raise the question I've looked again. Over about three weeks the Google click counter shows 18.5% more hits than hitslink, though my data set is much smaller than yours. And, when I look at my actual logs, they appear to match the hitslink stats. I've written to adwords support. Now let's see what happens next.