After 1 month with them
I've bought this headset and to be honest I'm hard pressed to fell the difference between ANC being on or off. There's a slight hum and the lower frequencies are a bit muffled but as this is my first experience of ANC I don't know if this is expected or not. If it is, I could live without it. If not, it's past the 15 day period.
Also the H800 (my previous headset) seems more comfortable to wear, although I've gotten used to these.
Two simultaneous Bluetooth sources connected at the same time is nice although it can sometimes (not often) get confused about which one is the active one if you're listening to music on one channel and just about to start a conference call on the other, which is not what you want.
I'm told it sounds a bit faint on the Mac but not on the PC. My Mac's WiFi/Bluetooth chip was replaced as well. So no idea who's fault this.
It comes with a dongle which you can use to connect instead of Bluetooth if you want. There seems to be a even pricier Plus version which works with some super special dongle which works with other Logitech peripherals at the same time instead of one dongle per peripheral but I see no need for this as only laptops have few USB ports and if you're connecting using a USB dongle instead of Bluetooth you're probably only plugging in a headset anyway.
So, yeah, they work and they're a bit pricy.