I checked Google analytics stats today for both sites, and from Nov 15- Dec 15 there were a total of 516 unique visitors redirected to the mobile site - about 29% of total visitors. (This figure has stayed pretty consistent since the beginning because I was checking stats along the way.)
When you talk to clients about the importance of a mobile website, let them know that chances are good that there are about 30% of potential customers that are finding them on a mobile device. If they don't give them a good (and fast) experience, they will most likely find someplace else to spend money.
Oh, and the most visited page after the home page for my client? Coupons! Be sure to have a coupon page on your client mobile sites so customers can show the coupon from their phone when ordering.
I expect my stats for the mobile to increase next year. Be interesting to see how it changes over time.