Anecdote
Here is my recent experience with an installer, after I ordered directv online:
He arrived at the appropriate time, but took 5 hours to install. He did not properly set up the network, so that tvapps & network services would not start. I have fixed that.
The biggest problem is that he was unable to get a picture on the SD television in our bedroom. The reason is that he didn't know the difference between component (Y/Pb/Pr) video connection and composite (yellow) video connection. I fixed this in about 30 seconds. I later talked to him on the phone, and explained the mistake he made, and how I corrected it, but he admitted that he still didn't understand.
It seems to me that this should be part of the basic knowledge for someone who installs any type of tv service. But, over the years, I've learned that no matter what TV service you are getting (and I've had cable, directv, dish and even voom if you remember them), I normally have to fix it after the installer leaves.