I’m using the ECommerce Services in a current project, using ruby-amazon. My main use has been to fill a local model with data from amazon, and I set that up as a plugin (dependent on ruby-amazon):
http://jystewart.net/process/archives/2006/07/loads_from_amazon-ruby-on-rails-plugin/
http://projects.jystewart.net/svn/rails/loads_from_amazon/trunk/
I’ve been working on integrating with the Pro Merchant API but ran into a few problems that i haven’t had time to work through yet.
James.