There's a neat thread on WebmasterWorld about what makes good traffic for an AdSense publisher. Nice to see a positive thread about AdSense!
Netmeg breaks it down into: traffic that purposefully visits your site, sticks around for more than two pages without bouncing, visits multiple times, comes from an authoritative or relevant link, and is relevant to your niche and location. Netmeg also writes that, "I want to put 'traffic that converts for the advertisers' but I also don't."
User IanTurner adds that traffic in an "age bracket [of] 18 - 65," is better because "Children are lower quality traffic as they don't have direct spending power." Working hours and office traffic are also things that they value.
"Also note that what's good quality traffic for YOU, might not be good quality traffic for AdSense purposes," netmeg adds.
What do you think makes good quality AdSense traffic?