I have placed an ad in B&W and it drive up the traffic to the site. But so did getting the article published last Falls in Black and White (Alisa's Mag). That brought a much bigger spike to the traffic.
The ad did bring a couple of print sales. Would have I gotten them otherwise? The sales from the site have been in the toilet since the economy went south. But it still pays for itself.
I have had the same problem as Thomas with people trying to sell me stuff from the ad. But you could look at the bright side even the people trying to sell me stuff saw the ad. That's a good thing.