@ChrisSCR 

I made the same conclusion, after one day. Like you, I'm working from home and my office is a bit of a dead zone, all printers / NAS / iMacs are wired but try using your iPad or iPhone and we had no WIFI, when the two of us are fighting for bandwidth it just didn't work. So I decided to splash out on the Deco's to compliment our trusty MR600 that has been working flawlessly for a year or so.

The first thing that struck me on opening the box was how well the product was presented, then I did the cold set up before powering on the devices (we one anyway).

Then the crap started. TP-Link account to use the App, what? OK I'll forget the app and just use the web interface, TP-Link account to use the web interface?

Ok, I'll set up an alias email ccount set the units up then delete the crap out of ANY TP-Link related bloatware / snoopware. (For what it's worth I do not and nobody should trust Trend Micro to provide "Virus" protection, they have been caught spying numerous times).

Ok, I'm setup, lets go to settings. There are none!!! Literally NONE. Oh wait, I can turn the LED off at night?

I just want these to work as a "MESH" to my continue my existing TP-Link WIFI. Oh, it's not compatible? What? This is a premium product thats not compatible with thier OWN mesh system? What?

Right. So I kill the WIFI on the MR600 and set up the WIFI on the dumb access point. It still needs a TP-Link account to do this? Why? Once running as an AP, you have litterally no control over these units, only the basics; WIFI name & password; Turn LED's on / off. A joke.

Some basic and I mean basic network tests show this thing is calling home... Why?

In summary, the hardware looks on paper to be promising, the software is a fiasco, the attitude towards customer privacy is shocking.

This morning I am returning these to Amazon to be replaced with Netgear Orbi's.

@ChrisSCR I have the same issues. Particularly iPhone loose access to internet constantly. WiFi still showing just access block. I have tried everything I can think of and nothing clears it. Just a piece of junk. Tried calling TP-link support and no answer, emailed them, no answer, tweeted them and they asked me to DM them, no answer, speak to someone on chat and they basically tell you to reset it and move the slave to main. It's totally useless. 

Well these pieces of rubbish went back to Amazon. TP-Link NEVER again. I am looking to get an alternate for the MR600 units next.

The Netgear Orbi's arrived this morning, all set up within 30 minutes. NO ISSUES.

No app needed to set up.

No online access / registration to set up.

Web access to settings.

Working as a bridged Access Point / WIFI network.

Stable & uncomplicated.

NO tie to Netgear. No email address required for anything. Registration optional.

Anonymous.

@CasaP no powerline though. Yeah I'm about to send mine back. Supposed to have been forwarded to senior team for solution and heard nothing. Joke. 

My P9s have been sent back as well.

I ordered a graded Devolo Magic 2 Wifi whole home setup from Amazon which arrived on Tuesday.

It was dead on arrival, having a fault with the main unit, so that has been sent back as well  The plug in powerline wifi units were very large and ugly, so I am not going to reorder.

I'm currently testing a Huawei wifi Q2 Pro set up. Not as fast powerline speed as the Magic 2, but so far it has been rock solid. Unlike the P9 firmware, I can see which mode is being used to transfer data between the units and what the speeds are. The 2.4 & 5 ghz wifi can be configured with different names and it supports mesh roaming.  There also appears to be a lot more manual intervention capability with the router as well. So far, so good.

Edit :

The Huawei setup has also been playing up with dropped connections, intermittent slow powerline data transfer speeds and other issues. So I have sent this one back as well.

My conclusion from all of this : 

No manufacturer seems capable of providing a reliable high speed mesh wifi system built around a powerline backbone!! Until they can, I have reverted to using some ancient 500 Mbps Homeplug AV1 standard plug in units. A combination of a Devolo sender unit and two Solwise receiver units, both of which provide wifi.

I don't have the luxury of 2.4 and 5Ghz wifi, guest wi-fi availability, mesh roaming, etc, etc, but at least they are bomb proof and do what they say on the tin. Hopefully some day, TP-Link or AN Other can figure out how to make a reliable and stable system that works as it should