The biggest turn off for me is that most UBI advocates seem to have the opinion that people freed from jobs will turn into philosophers or artists or otherwise make productive use of their time. I argue you don't really have to look very far to find the answer to that question: check out what an underemployed ~25yo from a small rust-belt town is up to. Chances are not a whole lot.
That's why I'm really in favor of a scheme like this. Ensure that people supported by the community at least give something back. Go a step further and increase funding for the arts so we can create jobs there too.