I have 2 of these. They are stupid expensive but do work. I see a squirrel on them once a month or so but they are soon frustrated and drop to the ground below after getting nothing out. They only get seed that birds drop. It got to a point that I'll see 2 to 4 on the ground searching.
The down side is you end up with far less ground feeders. Sparrows, Easter Towhee Mourning Doves, they normally benefit from other birds dropping seed as they feed above. But far less is dumped so you have less ground feeding happening.