I've never had much luck using it. Always provided tons of exposure for the program, and NO return. I hear it works for some folk, but not me.
For what it's worth, Amazon used to be a LOT better before (a) used books showed up, and (b) everyone had it! My stats varied over the past five years, but in essence, though my site has grown quite a bit, my Amazon is roughly constant or declining. It used to be about $100-200 per month; now it's just over $100 per month and more consistent. Lots depends on how you do it. A simple banner got me, um, nothing. I have selected text links with little reviews in a page of their own and on relevant pages I also have some chosen links. But I'm not adding new ones any more...return just isn't there. Over time it does add up if you get a good one, but predicing the good ones is hard. On a CPM basis it's pretty pathetic compared with Google. One question is whether there are lots of used materials for sale, because you know they sell used books starting at a nickel or so with $4 shipping... no commission worth mentioning on used materials most of the time. Toys and electronics aren't bad. Sometimes you get a guy who makes a BIG order through your site and that helps. But max I've gotten from them in a month is probably $220 - and I've been with them since their first year. Your mileage may vary. Indeed, I strongly believe it WILL vary. PS> I've been operating as a hobby since 1993-94. When I started out, I was incredibly happy to have my first thousand visitors/month and even ghappier to get $30/month to pay for the ISP. Now I'm at 500,000 visitors per month according to Webalizer...
I think selling a few books (or whatever) on Amazon is a good wholesome looking thing and helps people trust you more when they're looking at your other stuff that they initially do not trust so much. Even though it's great.
You need to sell like 10 million dollars if you want to earn enough comission to take your girlfriend out to the movies