I've had it less than 10 minutes...
...and it's already well worth its price. My kitten has more energy than she knows what to do with (play for an hour, sleep for five minutes, play for another hour) and I was struggling to keep up. I put this toy down in front of her ten minutes ago and she won't even acknowledge my presence. She's enthralled. If you have a kitten or a cat, you should have one of these.