It's an interesting concept, and I'd like to see more of these experiments to determine the validity of it. However, I find it rather interesting that the government did such an experiment, then locked it away top secret for 35 years. That makes me think something is fishy.
A basic income guarantee financially could work because it would ideally replace all welfare, social security, and other social programs to finance it. My biggest concern however has always been the motivation to work. I think it needs to be a small enough amount that you can only live very, very minimalistic on it without working.
Most of the suggestions here in Europe have been about 1,000 euro a month per person, which would put me and my wife at 2,000 euro a month, which is enough to live very comfortably in the area we live. I personally wouldn't work, I would do my own thing if I got that much. Who would work at a grocery store for chump change when they can live comfortably while not working at all? You'd have to raise the pay for those jobs substantially to attract people off their couches, which would cause prices to increase.
I feel if it's that high, many people would choose not to work. If even 10% of the work force decided to stay home instead of working, the repercussions for our economy would be catastrophic.