Most people buy Google phones specifically because they want Google to remotely manipulate their phones as quickly as possible with the latest Candy-named software. It's an in-demand feature.
I think that in practice, that applies to only the privacy sensitive features. Would you be upset if suddenly they rolled out a feature that reduced battery consumption by 10%?
This particular case was obviously a bug, but I suppose every software manufacturer is continuously doing A/B testing, and 99% of time the user would not even notice. I would be surprised if Google was not doing A/B testing, and did not have the whole framework for doing it.
If they secretly installed it, of course I would be. It's not like this is the only way to deliver features...
On live (not beta), unsuspecting users, without their consent?
If you're talking about battery saving mode, I would be upset if they activated the feature (turning it on) without my consent, yes. I don't have issues with Google pushing improvement to their code via OS updates.