Of dozens of programs I've tried, it was my top-earning one for many months. It also pays for click-throughs. Of course, high commissions alone are useless if people don't buy when they reach the site. As well as using products and services which match the theme of your site, it makes sense to experiment and see what interests your visitors. I haven't had much luck with that one.
People tend to visit several merchant account providers before they sign up.
However, AIS also sells various other products and services, which I've done extremely well with. These are The iLynk Wholesale Network , which would probably suit most sites, and Secrets To Making Money On The Information Super-Highway , which is good for sites offering Net marketing advice. See details on my Top 10 page. It's no good having a good product and a high commission unless you also have good salesmanship. That's why I'm really keen on Marlon Sanders' The Amazing Formula.