There's a single reason anyone buys a mesh networking system, and it's to improve what they can get from their existing, typically ISP-provided Wi-Fi router. The Google Nest Wifi combines both 2.4GHz and 5GHz into a single channel, which is simple, but it does mean you lose that choice if you know that what you want is on a specific band. Mind you, simplicity is very much the name of the game here.
I do have to give Google plenty of credit for making the set-up process of the Google Nest Wifi exceptionally easy. It's all handled through the Google Home app for Android or iOS, and it's as simple as launching Home and looking for new devices. Once the Nest Wifi router is spotted, you scan its QR code, tell Google Home what you'd like to call the network and the password you'd like to use and then sit back while it handles configuration and updates. It was even smart enough to realise that I was scanning the QR code from the two-pack variant of the Google Nest Wifi and prompt me to set up the Nest Wifi Point once the router was configured.
While the core router does indeed replace the Wi-Fi functionality of your existing home network, it's important to realise that the Google Nest Wifi is in no way any kind of modem, NBN or otherwise. You'll still need to use the modem part of your ISP supplied router – or any other modem of your choice – along with it, optimally disabling your existing modem-router's Wi-Fi routing functions. Google can't entirely help you here because of the variety of models on the market, but that also means if something does go awry, your ISP may ask you to step back to just its equipment because it can't troubleshoot Google Nest Wifi either.
There's a difficult point in testing any Wi-Fi equipment simply due to the variable nature of radio signals. Quite what I get in testing is specific to my own office situation, and your own points of interference could be quite different.
I've used the same home office environment for all of our mesh and extender testing over the years, with one close-by test spot, one spot two rooms away and then a "far" position that brutally tests any Wi-Fi network because it's located in my home office which sits on an extension to my property. That extension hides an original external brick wall that just loves blocking Wi-Fi signals. Your own layout may vary widely, but it gives me a good impression of both small home/office (the close and midpoints) as well as larger property or difficult signal areas with the far point thrown into the mix.
To test the Google Nest Wifi, I ran it through the same tests I've used for other mesh systems, first of all testing RSSI (Received Signal Strength Indicator) to check signal sharing and strength. Here's how the Google Nest Wifi compared to a wide range of available extension and mesh products:
That gives an indication of how well the signal is propagating and being shared between nodes, but then there's the question of what you can do with that signal. To test that, I used Finder's broadband speed test using an Aussie Broadband 100/40 HFC NBN connection. Here I was more limited in the range of test devices I could use because my prior tests were all run on a Telstra 110/5 HFC connection. For comparative purposes, I tested with my standard mesh system in this environment, which is the three-node Linksys Velop. Here's how the Google Nest Wifi compared:
That far figure isn't great, although it's doing better than I could manage without the extension Nest Wifi node in place. It's not quite a like-for-like comparison, however, because the two-pack Google Nest Wifi is substantially cheaper than the Linksys, and I could conceivably add a Nest Wifi point in my usual mid spot that should pump up the output across the mesh network markedly.
However, if you are looking at just the two-pack variant, be aware that longer distances or very difficult Wi-Fi connectivity isn't its strong suit; a third node would be recommended. While again, it's not quite like-for-like, the Google Nest Wifi compared favourably against other two-node solutions I've tested in the past.
What the Google Nest Wifi has that none of those systems have is an integrated Google Assistant. This is built into the Google Nest Wifi points only – and not the router – with a simple speaker and microphones that act very much as though Google's bolted a Nest Mini into the whole affair. You can mute the microphones if you don't want the assistant features. Audio output is, rather predictably, not up to par with, say, the Google Home Max speaker, but for essential queries or some rather light music playback, it's perfectly adequate.
Keeping with the simple ethos, Google doesn't offer a whole lot of network configuration options beyond speed testing and configuring the audio settings for any of the Nest Wifi points. If you're after a mesh router to run precise configurations on for your own reasons, this won't suit your needs all that well as a result.