Our house isn't bad for wi-fi (no thick walls or large area to cover), but was never good. The main router is in our study, in one corner of the house, and needed to reach four bedrooms, a conservatory and the garden, and reliably stream YouTube and Netflix videos.At first I had the wi-fi signal boosted by a wi-fi repeater. This worked sporadically for the past four years, but often the family would complain that they couldn't access the internet even though they had a wi-fi signal. Switching the repeater off would fix the problem but then left us with a weaker signal.So I decided to take the plunge with mesh wi-fi, especially after reading all the reviews about how it improved people's connection problems. These things can costs a lot of money (compared to my £30+ existing router), so I went for the TP-Link Deco M4 (3 pack) for just £100. This was a good compromise - cheap, but with a lot of features and good reviews.Setup is easy. Everything is done systematically from the smartphone app, so no silly faffing with web browser addresses. From reading other reviews I was expecting the smartphone app to assist me with optimum placement of the units (such as a signal strength guide), but all the app does is suggest putting the units in clear space away from large electrical appliances, which is pretty obvious!I wired the first unit into my main router, making it the main mesh unit, and turned the router's wi-fi off. The second unit was placed diagonally across the other side of the house near the conservatory (giving a good signal in the garden), and the final unit placed upstairs in one of the bedrooms. This seems to have everyone covered, especially our Samsung smart TV in the bedroom which has a very poor wi-fi receiver.There are two options when setting up the system: either full router mode, or as basic wi-fi-access points (with the original router continuing its usual network management role). I tried the access point mode initially, but that losses a lot of functionality:- No bandwidth usage monitoring- No Quality of Service controls- No parental controls (my son doesn't understand that internet use at 2am is bad for his sleep)- No Alexa integration- No IFTTT integrationSo I tried router mode, which gives me all the fancy gizmos in the smartphone app. This appears to work OK, although it can cause connection problems with 'double NATing' (where both the router and mesh wi-fi try to control how network addresses are accessed). There are two solutions to fix 'double NATing':- Switch the original router to bridge mode, effectively making it a dumb ISP modem, and letting the main mesh unit perform all the router tasks.- Put the main mesh unit in the router's DMZ, bypassing the router's NATing. This can be done in the router's settings.I decided to put the main mesh unit in the DMZ. This is mainly because I also have a remote access point (RAP) to access my work's network when working from home. The RAP needs to connect to an active router via ethernet, so I had to use the main router with all its spare ports (the mesh units only have two).Even though my original router is 'behind' the mesh unit it is accessible via its original IP address, so I'm still able to manage my ISP connection and other important settings.The system works well with my existing powerline adaptors too. My son's PC does not use wi-fi, so needs a wired connection. So too the Sonos speaker in the kitchen, which suffers from interference from the microwave. The Deco M4s can use 'ethernet backhaul' to connect together, giving a faster connection between the units. If I had purchased one of the Deco P range I could have used the powerline adaptors for the backhaul as well, but as the wi-fi backhaul is adequate I'm not fussed.Previously it had been mentioned by others that there was no web browser access to the Decos. It looks like that has now changed. The web portal can be access via the IP address of the main unit, using the same password used in the smartphone app. Bizarrely though, there are some things that can be done in the web portal, but not on the app, and visa-versa:- The web portal shows how clients are connected (wireless or wired)- Only the web portal shows the system log and time settings- Only the app can be used for adding units and users, or setting QoS and parental controlsA web portal is available from any of the unit IP addresses, but the satellite units have even less functionality.Alexa integration is a bit of a gimmick. The options available are very limited, such as (de)activating the guest wi-fi or turning the LEDs on/off. It's clunky as you have to instruct (and then wait) for the TP-Link skill to launch before starting any mesh instructions. IFTTT integration is also limited in its use for me. Most IFTTT applets just notify or log when a (new) device connects to the network.So far, so good. No lost connections, and smooth seamless switching between units as we move around the house.