Respectfully:

1. "It encourages the poor to work"

Extremely foolish. The poor don't work far more often because they can't, not because they're lazy or don't want to.

"...current US system penalizes the poor if they work"

A little, but this is way, way, way overblown.

Also like I said elsewhere: one of the key points of universal income is the libertarian small government aspect. Half the point of a tax reform is to save money, and cut down on corruption, a negative tax system will explode those two categories.