I just switched to this router as well. The 5Ghz band is great, solves my LG G4 not being able to reach 50Mbps while on the 2.4Ghz band. I feel that the 2.4Ghz band from this router does not improve in terms of range as 2.4Ghz devices on the second floor still receives only half the bandwidth. The 5Ghz on the other hand can deliver the full 50Mbps speed most of the time on the second floor.

The switch to an AC router is worth it if you have devices that can utilise the 5Ghz band. My 4 year old laptop cannot even use the 5Ghz speed, only my phone is 5Ghz capable so the switch to AC router did not do much good for now. If you have a lof of devices that can use the 5Ghz band I think the switch will bring about a better experience.

Same here, went with Aztech Homeplug and use LAN instead as my Wifi USB Dongle upstair gets weak signal and keeps disconnecting as well as getting too hot.

I actually meant upstairs I get about half of the speed, when I am standing next to the router I get around 45+ Mbps speed from a 50Mbps internet connection.

The 2.4Ghz band of the 1200G+ is limited to 300Mbps (Mega bit), translate to (Mega Byte) is 30MBps. The Unifi speed of 50Mbps translates to 5MBps. With me standing next to the 1200G+ and the unifi router provided, I cannot hit 50Mbps speed on my phone. With the 5Ghz band I can.

The 2.4Ghz band is just strange for me, I did not notice or care for much about this problem before the upgrade as I was mostly using LAN. With the 30Mbps speed before the upgrade, getting around 20Mbps upstairs, I did not think the loss was too great. But with a 50Mbps speed now, the loss is more than half of that.