I like the workflow for creating stacks and I really like the polyglot nature of selecting which cloud to deploy to.
They did have a security incident a while back and I'd recommend reading up on that. They had a blog post about it but it appears they've since pulled that. I don't know what that's about.
I'll tell you that you'll be hard-pressed to find better customer support/service in another company. They're open to suggestions and will help you if you ever run into an issue deploying an app.