One thing I like about this concept is that it's based on people creating public space on their private property. They are well maintained, aesthetically pleasing, but also quite eclectic. Since these are typically set up by individuals on residential property, they aren't just token efforts – they aren't a disingenuous attempt to prove the person is community-minded (though I'm sure appearing community minded is a motivation, it's just not a disingenuous motivation ;)
I wish there was more of this. I'd actually like to put a bench in my front yard, facing the sidewalk – unfortunately people would use it to congregate and drink. But then, so it goes – there are other people near me who wouldn't have that problem, because these problems are typically block-by-block. For some reason my yard appears like a perfectly good drinking spot, I'm not sure why, but I am very aware of it.
When benches are put in by the city, the person who makes that decision is not at all aware of these specific issues. They don't live with the result of the infrastructure they create. So we have another public bench near us that causes problems. Or often there are no benches available because they are seen as a nuisance, or the public space is rendered hostile in some fashion to discourage loiterers, which simultaneously discourages all enjoyment. These are the crude choices cities make because the people planning aren't intimately involved with the specific environments they are affecting.
(If I ever do something with the hill in my front yard I think I'd like to install a slide. I think that would be enjoyed but not abused. And if I'm wrong I'll have to figure out myself how to fix it)