So far my AX3000 has been rock solid, it took 2 attempts though, I left a review on Amazon, it's not a deep technical review or anything, but it did solve by WAN bottleneck.
This review is going to concentrate on WAN and CPU performance, there are many reviews on WiFi performance, but that was not my issues, and there seemed to be scant information on WAN/CPU performance.
Quick tip, of all the Asus features, enabling QoS is way and above all the other features with regards to the extra CPU power it will take once you enable it.
I have around 70 devices in our 2700sq ft home (I have extra APs around the house), security cameras, VMWare servers, NAS, multiple Firesticks, kids with phones, tablets, game consoles etc etc, so a busy network.
AT&T BGW210-700 in passthrough mode - PC plugged into LAN port on AC1900 - best speed I ever got was 180 - 320Mbps.
Also, when running speedtest one of the 2 cores would max out at 100%.
Disabling some of the Asus threat preventions features would increase the throughput. For example, disabling QoS would give me a 20Mbps -30Mpbs boost, if I then disable the traffic analyzer, got another 10-20Mpbs boost, and so. And ran these tests many times over different times and days, and it was very consistent.
This led to believe that my throughput was CPU limited, and time for a new router.
The first AX3000 was pretty much DOA, lights would come on, but it would do nothing, so returned.
Several months later I thought I'd try again, and this time it worked without issue, and now I'm getting 900-930Mpbs without any of the features turned on, when I enable QoS and the such it does still drop, to around 500-600 Mbps.
Also, with no features enabled, when running speed test, 2 of cores go up little, 10-15%, and the a third core goes up to 50%.
I then enabled QoS etc, and 1 core is still between 10-15%, and the other 2 cores go up to 30 -50%, so some capacity there.
The extra power in the new CPU, higher base frequency and more cores seems to have fixed my bottleneck.
I wanted to preserve all the static IPs I have and Asus made this simple, I exported the configuration from the AC1900, and then imported into the AX3000, rebooted, logged into BGW210-700 and assigned the new target MAC address for the passthrough and of it went, easy peasy.