This review is specifically for the regular powerball.
This powerball does NOT include a counter.
Yes, you probably were already aware of that, as I was, but are thinking "how much more could that possibly add?" - I owned the powerball for minutes before I wished I had spent the extra couple quid to get a counter included - it really does add that much more enjoyment and seriously lengthens it's "enjoyability". You CAN buy a counter separately, but this is almost the same price as the powerball itself, so essentially I am just URGING you to get the counter included.
The ball itself is... interesting. Doesn't take too long to get the hang of it (at least it didn't for me, there are still several friends of mine struggling to start it every time they want to "play" with it) and you really can feel the strain when you do it correctly (you get most benefit almost holding your entire arm still and forcing yourself to use only your wrist).
Instantaneous effects are a dead arm and a bulging biceps (fun fact of the day: the biceps is mostly a supinator of the hand, not a flexor of the arm, hence it is worked out with this gadget). These effects are short-lived though, so don't expect to look built simply by using this - you'll need a real workout for that.
Grip has improved considerably and tendons in my wrist are rock solid so I will continue using this but the original point still remains...
GET A COUNTER!