Back to Hugo's original question (which IS about plastic as Stefan uses in the permaculture orchard video), Stefan was using an exceptionally thick plastic mulch because it had a much longer lifetime than the usually used plasticulture. Stefan also pointed out that organic mulches didn't work for him and my experience is in line with his. If you need to mulch any sizable area (i.e. larger than a small garden), you will spend large amounts of money and time on the organic material mulches. The weeds will almost certainly penetrate the mulch in relatively short order and you will spend your time dealing with that problem. If you have a small orchard like Paul Gautschi (sp?) in the Back to Eden movie, then mulching with wood chips or other organic material will work well. I totally agree with others posts about the benefits of organics and the drawbacks to plastic.
The black plastic will definitely heat up the soil. If you can only find the thicker plastic in black, I'd suggest some sort of whitewashing (maybe a lime mixture?) to reflect the light up to the plants. I have had decent luck using landscape fabric on top of the soil for annual vegetable production. I burn holes in it for the plants and pull it up at the end of each season. I am on my fourth year of reusing the fabric and it has drastically reduced weeds and help plants grow in my relatively cooler climate. The weave of the fabric allows rain water and air to penetrate and the cover helps keep moisture from evaporating from the soil. Any time I have pulled back the fabric, the soil beneath is teaming with life. I do not recommend using the fabric underneath another mulch, but have it on top of the soil. As the plant canopy grows out, it shades the fabric and I think eventually the extra heat isn't an issue.
Best of luck!