Regarding saving as-you-go, I would follow the Google way, just informing user that "All changes are saved in Drive.".
However - there is one kind of actions that I would add "save" to, so that it would make users more comfortable. I assume that the question "Is my document (or: whatever else) saved?" is asked by the user whenever s/he tends to leave it - either when the job is done or when s/he cannot keep working on it at the moment. Thus, if there is any button that allows user to leave the document ([Quit], [Exit], [Close] or anything leading to logically different area, like [Preview]) I would just change the text on it to [Save and quit] or [Save and preview] (even though it is almost obvious that work is saved before previewing). I would just skip the actions that "fork" from the main path - like printing for example, or exporting - these do not affect the main use flow usually, of course everything depends on a specific system.
Interestingly, I find this necessary only for people at some age, these who remember applications that could work this way - I mean closing without saving or even without asking to save something with ongoing changes. I believe that people younger than, say, 30 years, will need it significantly less than the older ones. But this is just guessing. We come from vairious points in techno-cultural space, severly distorted along its t axis. So everything needs to be tested - without it "I can only say what I think users think", as someone said ;)