Well I have a different point of view.
I drive a 2001 F250 SD with a 7.3L motor. I have been running a chip or tune on it most of it's life and I have put every single mile on it, now at 222,000.
My ECM failed several years ago due to a known factory issue and after replacement I did not re-install the chip. The truck was a slug but I left it that way. Average mileage was about 15mpg (average). Ran OK but not like it did before.
I recently decided to tune it again because I am towing again. It was the best move I made. The truck runs great again, I am getting about 18.5 mpg over about 6 tanks of fuel now and it is more responsive and runs smother. I of course do not have a Dino at home so measuring the HP increase is not possible, but it will again get up and go like it did years ago.
I went with a very simple and not to aggressive tune, the device I used is made by Hypertech and it is the MaxEnergy 42500. Here is a link Error - Hypertech
I found a used one on Amazon for about $250.00. I figured if it didn't work I would return it.
They have 3 stages of tune. I used stage one which claims +32 HP. I definitely feel and see a difference. I tried Stage two which is more aggressive and I did not like the way it shifted and with almost a quarter million miles I didn't need to put that strain on my tranny. Stage 3 was not even a thought.
Amazon has 2 more used ones online now at $263.00.
The tune is easy, first it backs up all your factory settings, then it loads the tune. You just plug into the OBD port and follow the onscreen instructions. The first Tune took about 10 min's to gather all the info and load it and the second one was much quicker.
The device also told me about a few trouble codes that were stored so I could look them up. Mine were old, I cleared them and the tune loaded easy.
Bringing the new TT home was a breeze with the way the truck pulled.
I hope this helps.