I bought a couple of the ones from the eBay guy a while back for my game.
Firstly, the guy is a good and reputable seller. The balls are very nice quality.

Second, the balls are the same size, but DEFINITELY lighter than a steel ball. The play is much faster because of it. It's not a thing where you'd have to compare back & forth to tell the difference - it's very obvious. Holding the ball, it feels pretty heavy, but then you pick up a steel ball and you can feel that the steel is heavier.

I think if you try it in a game (doesn't have to be a TZ, any game will do) you will notice the obvious speed difference and probably enjoy the temporary change of pace and challenge. It takes a whole different timing to play the ceramic ball so things get all shook up, which was the original idea.

The only "revision" of the powerball that I've heard of is the color. They originally made a blue one I think, but it was too hard to see so they went with white.