Its a code evaluation platform, running containerized under the hood, and with a large markup by Amazon. Companies have offered this for years before AWS, but AWS is tooting the horn louder than people have before.
Is it useful? Yeah, sure. Is it revolutionary? Oh come on now.
Just like "the cloud" is just timeshare on someone else's computer, this is simply code management and execution abstracted a few more layers up.
EDIT: Sorry I'm not on the hype train folks.