I use it on a number of my domains (currently 7-10???).
I started using AOM just as Amazon dropped its starting percentage to it's current rates, 4% for US affi's and 6% for UK sites.
Though the Amazon's percentage has dropped quite a bit in the last couple of years, I've covered my upfront costs for the "Pro" version of AOM and expect to continue to cover the yearly "maintenance" fees ($20 USD) plus a few added $$$'s -- but not a lot.
If you have a high dollar product niche, know how to SEO and can spend some time customizing the sites a bit, you should do alright.
Personally, my biggest interest in AOM is the fact that it can help build traffic and a presence in the search engines thus increasing overall value of the domains that the sites are built on.
Be aware that depending on your domain's product niche, sometimes it's a bit tricky getting the settings "just right" when you are building each site. Though I'm no AOM whiz-kid, I've made enough mistakes and have learned a few things so feel free to PM me if you think I might be able to help.
Also, there are a few people over at the AOM forum that REALLY KNOW how to customize their sites. Many of these customized pages/sites hardly even look like they started life as AOM. Speaking of AOM forums, they are very helpful and friendly -- just like here at NP!
I think there are some "developers for hire" who use AOM to build "custom sites" for their clients. An example of these types of sites can be found over at Latonas.com where there is an auction going on for "100 developed keyword domains" that all start at $250 min bid. I think all the "product" related domains in that batch are built on AOM.
Good luck!