I have a somewhat lively class, but as soon as they hear someone getting a reward they all want one, trying their best to get one. I love it. Simple as that.
Another good feature is that it gives you a details weekly/ monthly/ yearly breakdown of behaviour. It gives you a percentage based on total rewards/ sanctions. If my class have a week above 95% then they earn a class star. If they earn 30 class stars, they earn a pyjama party, a goal they are very keen to reach. We also do a lucky dip- where the pupil with the most points that week wins a small prize.
Oh yes... it's FREE! Check it out.