I've done a few of them, but in all honesty there's very few of them offered close enough to home to make it worthwhile. Hubby works in the city & he's done a few.
A few years ago there was one that gave you a bag of groceries and a small gift card (about $30, I think) for attending. I wouldn't normally be bothered, but they were just up the street, about a five min drive, so I did a few of them, but they must have got all their Western Sydney data now, & I haven't heard of them since.