I think they're neat and cool looking but "effective" may not be applicable to everyone. It's truly a personal solution. Depending on how good your eyesight is, the type of operating you do and the room you may have will all dictate what you can do.
I run with 3 24" monitors, all next to each other. Sometimes I still have a need for some additional screen real estate. My biggest concern with a large monitor would be those windows I place in the upper corners of the screen that cause me to stretch my neck or get up to read them.
Most programs these days will remember the window positions when restarted.
Also be sure the resolution is such that text is really readable on a 40" or greater Monitor.
The extra real estate is certainly welcome in this Flex world we live in.
I would be cautious using a TV as a monitor. Many have reported that they are, for some reason, not nearly as good as a specifically designed 4k monitor. Naturally, there is a cost difference! I currently use a Dell 30" 2560x1600 pixel monitor with a Dell 24" 1920x1080 monitor above it. They go together well, as the pixel pitch is virtually identical on both monitors, meaning things are the same size on both. It is barely enough screen real estate for SmartSDR, DX4Win, DDUtil, FRStack, LP-500, and a DXAtlas gray-line map. I have been thinking of upgrading to a pair of 32" 4k monitors, but it's not cheap -- about $400 to $800 per monitor, but prices are slowly declining.
I, too, had been thinking of a 43" 4k monitor, but ended up deciding that it is just too big for the reasons Joe mentions, above.
So, my advice is to make sure that the 4k TV is returnable, just in case you don't like it when used as a monitor.
I have two 27" monitors running 2560x1440. I just added a 49" Sony 4K unit.
The Sony looks great and sits above and behind the 27" monitors about 4' from my face. At that distance SSDR looks perfect but windows apps are on the small side so I run 125% screen scaling (most days) to compensate. It would be fine at normal 2' view distance. I would not want to run my main apps on the top of the screen (for neck reasons) and I prefer the flexibility of multiple monitors. For one you cant use the full screen option for videos, etc and still use other apps.
I just move things to the 4K TV that I need to keep an eye on. DX cluster, security cameras, and anything else that does not have my main focus.
And I agree with Craig, the 4K TV typically is not going to be as good as a 4k monitor. The cheaper 4K units I have seen are overlay saturated when used as a PC monitor. This Sony is not perfect compared to the professional Dell 27" monitors but acceptable and I am happy with it.
I like my LG 29 Monitor I can divide it into numerous screen configurations and I can have 4 1920x1080 screens up at once on one monitor. I usually put smartSDR Cat on the upper left, DAX on the lower left and then SmartSDR on the rest of the monitor all at the same time.
The LG app is great plus I have it through an HDMI switch and use it with 2 other computers besides the one I have dedicated to the Flex6400M.
If I had the room I would have got the LG 34 to put there, but I don't it will also do the 4 HD screens as well.
I had Quad 24" monitors in a 2x2 arrangement.... They were a pain the butt to use and set up, so I switched to 1- 4K acer 43" monitor. Lots of Real Estate, easy to set and drag the windows around to maximize the view..... Its a 4K monitor but the print is a little small for these aging eyes, so I stepped down the resolution, and windows 10 remembers the screen size boxes
73, Brian WD9HSY