Just wanted to put a fair review, against the negative ones. Our daughter had this today for her birthday, and I looked online for details of what type of cream to use. I found a load of negative reviews, here and elsewhere, and therefore tried not to get the kids hopes up.
However, when we used it we were surprised at how well it worked. We used double cream, followed the instructions (didn't even fill up the drum fully with ice cubes as we ran out!), and after 10-15 minutes of fairly relaxed turning, we started to get decent consistency ice cream to start scraping off the drum. OK it melted fairly quickly, and you'll never get the quantity shown on the box from one mix, but the kids had great fun, and the ice cream tasted surprisingly good.
So just don't expect too much, (if you want to make a large quantity, get a proper ice cream maker!), follow the instructions, use double cream, and theres no reason you shouldn't get half an hour of fun, and a couple of small tubs of decent ice cream out of it. BTW I'm nothing to do with the makers!