It took me awhile to get, but my aha moment was understanding its relationship to regular PaaS's (eg: heroku).

What more could you do if you didn't need to deploy your entire stack with each little change you make? If you could only deploy your frontend (in different versions simultaneously) pointing to a backend that's always up, it enables much faster iteration: testing, bugfixing, demoing things that otherwise you might not deploy different versions for because it's too painful.

For example, you could A/B test meaningful portions of frontend code in a more scalable way than, say, Optimizely. Or you might point a user that's having problems to a specific build (which you can deploy instantly) and see if it fixes their problem _on their live account_. Or you can hack together a new feature that works _on a live account_ for a presentation, and push it without worrying about mucking up or interrupting production traffic. Or turn off minification instantly and deploy that.

Plus, you don't have to worry about refining internal frontend build scripts, it's plug and play.