Temporary Cloud Storage Of Messages Betweenn Our App Users.

We are looking at a scalable cloud hosting sites for our app to allow allows users to post messages, read data sources and photos.  The Ansca cloud seems expensive

Has anyone tried the Amazon Simple Queue Service (first 1,000,000 messages are free etc):

http://aws.amazon.com/sqs/

Or has anyone connected the Google App engine ( https://developers.google.com/appengine/ ) to an app?