I've recently been asked to look into AWS' Simple Workflow offering, which appears to be a very specific model of working with a hosted message broker to embody a workflow. There's even an library of annotations that will decorate your classes with implementations to do the polling of its queues, and some interesting asynchronous functionality too.
There's quite an overlap with Spring Integration what with polling consumers and remotely-stored queues.
The API just isn't as nice as I'm used to with Spring though. Whilst there are some Spring-friendly helper classes, one has to code to AspectJ-generated classes, and all 'activities' (think @Services) have to be registered in XML rather than by package-scanning.
I'd be over the moon if SI wrapped some of the nastiness of coding to Amazon's API!