Funny you should ask Blumpy...I was wondering something similar. My stray gets wet and dry, and I used to see him drink pretty regularly. Since I moved last September though, I don't think I've seen drink any water, even once. I did start adding some water to his wet food - I don't know if that's the reason, or if it's because I changed his water bowl, or something else.
I know a lot of people don't worry about water intake if the cats are eating wet food, like NOLAKitties said. I worry a little because Mr. Casper does eat a lot of dry as well.