As there seems to be a lot of discussion about this taking up other threads thought maybe it deserved one all of it's own.
Personally I have had a couple of x2 Speedy thingys & a 25% Cashback Reward. Speed thingys just levelled me up twice which got me free spins which got me zip. The cashback one twit that I am, I managed to activate by accident when my balance was a massive £3 so clearly that was the end of that.
Even with my rubbish luck I have to admit it is one of the better promos currently about.