I'm not sure I'd put Google down as an omnipotent monster type organisation - although they certainly don't feel as happy/friendly/touchy-feely as they used to. I guess do-no-evil doesn't always cut it with the shareholders.
That said, my contacts with Google have mostly been helpful; but as others have said, the idea of relying on Google entirely for your business is not a sensible idea; that's just common sense (ie, not all eggs in one basket).
I don't think we're *super-successful* with Google, and I know we could do better, hence the opening question. We have built up a 6 fig annual turnover with them, but that said, they are just one of several revenue generators, and our costs per year (mostly hosting & development) are truly terrifying.
If anyone ever asks what we do/how we did it - the answer is pretty much the same as most other companies that has done something similar; good content, site designed with the users in mind, sticky content, lots of user-generated-content, etc.
Certainly in our niche, Google is not the biggest payer by any stretch; but it can deal with the volumes, so we use it as remnant 'overflow', and it's nice and consistent, scaled inline with the site traffic.
I haven't read through the case studies in any detail recently, but it was my understanding they never discussed figures anyway... Ho hum.