Useful info about copper sprays: http://www.nysaes.cornell.edu/pp/resour ... copper.php
I'm not a big fan of copper, although I will use it as a last resort if nothing else will work. In my experience it doesn't work all that well. Some copper products aren't approved by OMRI either.
Copper gets into the soil when it washes off a week or two after you apply it. It gets into the compost heap if the plant is composted. It does not break down or leach out, and it's toxic to earthworms and beneficial microorganisms that inhabit the soil in your garden. If the spray drift or discarded leftover spray reaches a stream or pond, copper is toxic to the aquatic life there (don't dump leftover spray down the drain!).
If you use a lot of it every year, it's a good idea to test your soil occasionally to monitor copper accumulation.
What kind of blight did the tomato grower say your plants had? Leaves fringed in brown sounds more like fertilizer burn or too much hot dry weather to me. Early blight or late blight would cause big dark spots on the leaves, not brown fringes.