I'm privacy conscious and bought a couple of minis. I don't use the mics but I thought I had a legitimate use case without one. It's falling short and I'm looking around for replacement devices.
I flipped the hardware mic switch off on it, to try to make it a dumb wifi speaker instead of a "smart" one. Then I built a software alarm clock that forces me to leave the room after I wake up in order to turn it off.
For me, it's very important for my alarm clock to be both effective, and to always work. The alarm clock runs as a remote task and connects directly to the mini, telling it to play an MP3 from the local network (by IP because the mini ignores DHCP DNS server). If I hit the mini touch controls to turn it off, the software starts playing a different MP3 a second later. If I try to unplug the cable from the device, duct tape stops me. Thoughtful wrapping of the cable around a solid furniture post prevents any yanking from being effective at tearing it out of the wall. If one mini is down (fairly rare but possible point of failure), the other one is attempted.
So, it's fairly impossible for me to just turn it off without waking up and giving it a bit more thought. I have to leave the room and tap a button on a touch screen (ubuntu in kiosk mode reaching web app on local network).
The unfortunately fatal flaw is that after months of effective use, I recently discovered that my highly available alarm clock was not actually highly available. It breaks when the internet is out. I could not connect over local network. There's always the possibility that something else was a factor, but I reproduced it a couple of times intentionally.
It also concerns me that the mini doesn't require authentication. Anyone on the local network can directly reach the device and do the same thing. A script meant as an alarm clock could turn into a device of psychological torment in someone elses hands. This lack of authentication, and the ability to auto-discover the speakers, is probably something they consider a 'feature'. I don't like seeing Chrome waste system resources in its attempt to scan my local network on the off chance that Google's speakers are there. And I don't want it to reach out to those speakers when it does find them. But it does it anyway.
In the end, with the microphone disregarded, it's a cheap wifi speaker. I won't count Chrome's bad behavior against it, but its software could be improved by offering (any) secure connection options. The lack of internet as a single point of failure dooms any kind of gadgetry with a reliability requirement from using it. It can't be considered reliable enough for serious tasks like waking you up for work or a flight unless they fix the software to work in a local-network-only mode. But, it is cheap, and, well, mostly available, which is often good enough for to-hand use cases.
Speculation: Is the lack of mini's heartbeat phoning home Google's own way of determining network reliability across wide geographic areas (eg, the lack of data in an aggregate area)? But they probably know this already from the wide spread of Android devices. Or do they maybe just not want their device to work unless it can reach back to them?