I've been using TP Link Deco M4R for 2 or more months na ata. The first few months are great. My setup is main deco is connected to 2nd deco thru lan and 3rd deco is connected wirelessly. Ung 3rd deco is located 10-12 meters away with a concrete wall in between. Yes, may decrease ung speed dun sa 3rd deco unit, dahil sa logistics nya and dahil sa concrete wall.
I would recommend you to check out other units out there. Recently, may problem ang firmware ng Deco units, take note, hindi lang siya sa M4. Nadidisconnect ako sa net and I'm getting high pings kahit naka connect ung desktop ko sa 2nd deco unit (which is connected thru ethernet sa main deco unit). This also happens with my other wireless devices like laptops and mobile phones. I've been active sa official TP Link Deco forum but it seems they don't have a fix yet.
Official Networking Thread (LAN Configuration, Internet Sharing, Routers, Switches, etc.)
^ Thanks chief sa info! My friend opted for the M5s kasi the M4s are always sold out. Wala pa namang disconnection problems however meron ng signal strength problems with wireless mode. Baka mostly dahil sa way pagkasetup and baka sa wall din. Plan ko na lang is mag iperf on common areas where they hangout para the reception can be improved.