Bangerjay has a Tron with 4 of them. Game is crazy fast.

I've seen it done for slower EM or solid state games. I've been wondering how it would affect atari games, myself.

I think a lot of people do it as an easy fix for weak flippers

Not sure. But if you're running a tournament and you don't have time to rebuild the flippers, I think it's a clever solution.

I have used the mini "cue ball" in EBD since 1993.

At "The Sanctum" they have had one in a Bobby Orr Power Play for about two years now. A piece of paper covers the backglass so it says Bobby Orr Power Ball. Pretty funny and makes the game a bit more lively.

I have been contemplating putting "one" in my MET premium to make things a bit interesting. about the only thing that screw the player is not being able to [lock] a ball with the hammer.

of course the graveyard and sparky magnets wouldn't grab the ball, but it also wouldn't prevent the modes from not starting after the appropriate number of hits.

Best place to purchase one?

$39.
https://bayareaamusements.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GS-TZ12
This has been the standard *absurd* price going on nearly 20 years.
$10 cheaper that Marco, though.

Sometimes you can get them around $10-20 used, but I have not seen many lately unless I did some hunting.

If you have connections in the ceramic bearings industry, you can get a whole boxful of 1 1/16" balls for probably the same price.
I have not checked in a very long time. If you are really creative you can still get other colors by special order (through a machine shop) just like the original sample games that used blue in TZ, before most were removed at the factory during testing. A number of very old owners of TZ have them in their games. I have lighter color blue one in the coin tray inside my machine, but as it was tested it was too damn hard to see the ball in the game, and I removed it.

Keep in mind, if you have a USED Powerball just use some Mother's mag polish, Flitz, or other proper metal cleaner and it will polish up like new on a buffing wheel in less than 10 minutes, unless it is has been severely damaged, and this is rare.
You do not need a new ball, and if cared for properly are fairly indestructible inside a pinball machine.
Buying a new one is just being lazy on money people do not need to spend.
My preference is Mothers or Flitz, as I have used both many times to keep my PBs shiny white, instead of dull grey.

I have a set of 5 power balls and have tested them in all of my games at one time or another. I usually just add one to a game and sometimes all of them.

Game play action is notable different on all games but not always for the better. They will defiantly make your games play faster and the ball action will be different. Which I happen to like, especially the different bounces and action.

But some of the newer games will often get air balls everywhere and hitting the glass is common. In some games, balls came off the flippers with such velocity and air, I've worried about breaking plastics or toys. In other games that need to be sped up, like EM's or Solid State, they work great and its fun to experiment. If the games have any magnets you can pass on trying them.

I've seen the powerballs installed at tourneys and HATE it!

I don't usually play in tourneys but will enter if there is a game I really want to play in the tourney bank. I want the game to play as it was designed.

GLO-Balls are the same weight as the original Powerballs and have a steel core so work with Game's that have magnets.
Have them in our CV & they're simply insane !

Put a power ball in my 1970 Williams strike zone, I have it 'dialed in' so it already played pretty fast, it made even this old EM play insanely fast. Fun for a change but took it out after a 3-4 months worth of play.