Actually, compared to all of my other gripes with Google services, I've always found their account management to be pretty coherent and easy to understand lately.
SSO on iOS across the browser and Google's native apps, and "sign in with Google" in 3rd party apps, works flawlessly for me.
The only thing I'm missing is a "sign me out" button (per device or even on all devices) that actually works.
As a person who uses at least two accounts (personal and work), and a third account on YouTube (I've had it since before Google Accounts), the number of Littles things that way consistently don't work is baffling. Well, you can see just one day's worth at the link :)
SSO on iOS across the browser and Google's native apps, and "sign in with Google" in 3rd party apps, works flawlessly for me.
The only thing I'm missing is a "sign me out" button (per device or even on all devices) that actually works.