With my clients, more traffic means more leads.
Actually, not true. Even for your client and I have no idea who your client is.
I guarentee that no matter what you sell, I could send you 100 visitors that won't result in a single sale.
Bill's point was that traffic doesn't always equal more sales. It's about getting people to focus on driving QUALITY traffic rather than simply "traffic." It's that old quality verses quantity issue.
If you are converting your visitors right now, then yay!
That's a good thing. But realize that the reason that you convert them is because you are bringing in visitors that are intersted in what you sell.
I'm willing to bet that if you dig a little deeper, you'll find that there are traffic sources that send you absolutely zero customers and that there are other traffic sources that convert at an amazing rate.