I used to be with e.on but when we moved house, we switched to EDF, which has better monthly pricing for what we need, but the bonus rewards are not as great. I used to love getting the Tesco reward points. I think I would have preferred the money to go off the bill, however, if the reward was equal to the clubcard reward. The company I am with now has a monthly reward draw but the prizes are for voucher codes with a conditional spend. I never both as the prizes are useless.
I love loyalty cars and reward schemes and think every provider should use them.
Having looked at e.on's scheme again, I kind of wish I was still with them. I might call and get a quote to match my current deal, just because I would really like this type of reward system again.