The seeds are like most parts of the solanum family poisonous.

They are, as Farm1 said, the way that new varieties are created. So you might like to try producing your own new variety (and make money) but, as thousand of seeds are sown by the professional raisers of new varieties to produce one good new one, finding the good one is like looking for a needle in a haystack and finding the farmer's daughter instead (a quotation from a Dutch potato specialist). So to say they "are of no value to the gardener" is not quite true.

If you want to try, sow the seed as you would half hardy annuals next year. Pot on the seedlings into 3" pots and then plant outside in May. At the end of the year lift and see which plant, if any, looks healthy and has produced the best looking tubers (they will be all be small). Grow these on in 2008 (throw away the rest) as normal potatoes and again check for quality of plant and tubers at harvest time. Grow on the best in 2009 (throw away the rest) as normal potatoes and again check for quality of plant and tubers. If, at the end of this year, you think you have a variety which has a better flavour, prodcues a higher yeild or is less susceptible to disease than any other current variety contact a seed firm such as Thompson and Morgan or a specialist organisation like the Scottish Crop Research Institute.