My cats (3 of them) aren't really interested in it. They go over once or twice a day, nudge it a bit. If I poke it, they get into it for a few minutes, then lose interest again.
All in all, a great toy. I set it up for the first time last night and it’s been played with a lot ever since. Just now, unfortunately, my two kittens managed to fish out the first ball. :/