In my case, I did connect it once to the internet, to see what's up, and since it had prime video which is pretty much the only thing I watch, it could have allowed me to not have a different box and cables laying around.

And, indeed, it started showing ads on the homepage and the UI was pretty laggy, even compared to my several-year-old firetv. Fortunately, I was able to do a full factory reset and it forgot everything.

Now I only use the software to switch to an HDMI input which doesn't handle the control bits, like a PC, and to increase the brightness in case I'm watching at noon and don't want to close the blinds. 90% of the time, though, I don't even know it exists, since I only use my set top box' remote to do everything I need (change channels and volume, turn on and off). The other 10% it works well enough that I can't really complain.