You can say how much money you have made from them total now (New change in TOS), but nothing more specific than that (As in: how much you made per day/site/click/etc.).
As far as how many people use Adsense that still have a long way to go to reach $100.... almost everyone still using Adsense found that it works for them, therefore most folks (That I know, I'm sure there are many that don't) that still use Adsense get very good returns from Adsense. Otherwise, making less than $100 a month isn't necessarily worth the time/effort.
-Allan