I want to mention that this feature isn't just about the convenience of auto-save. It's about the inconvenience of the save being a synchronous operation. When I save, I have to stop working while I want for the save to finish. I find this tremendously disruptive.

I'm sure there would need to be a lot of back end work to create an auto-save function, but it's becoming standard on many SaaS applications.  It's part of what makes working in the cloud so appealing.