Yes, my balance has climbed pretty quickly the last few weeks too. I'm getting bonus points on things I'd have bought anyway - in some cases, heaps of points on very cheap items. I got 100 points, which I'd have to spend £100 to get in a normal transaction, on a 65p pack of chicken slices. And you still get the bonus points if the item is reduced, so last week I paid 10p and got 80 bonus points.
And almost every time I shop (which is usually at least once a day, cos there's a Local two minutes away) I get the "rub for bonus points" thing, and only once have I not "won" anything.
On the downside, the "double up" option hasn't appeared on my app, despite deleting and reinstalling. Looking on Twitter, I'm far from the only one.