I can't quantify but in my home town, Moura, it had a good impact in local economy. They built there one solar plant with 46 MW capacity which was at the time the biggest in the world. (http://translate.google.pt/translate?u=http://economia.publi...) They also built a fotovoltaic pannels factory for constructing the solar plant and which now exports pannels.

Considering how bad every economic aspect goes there it was really a blessing. The jobs it created, qualified or non-qualified; the population it brought (desertification is one of the worst problems there). And they really deserve it, right now it might be 45ºC there. I work in Lisbon and when I occasionally go there in the weekend I can barely do anything(hint: fresh beer tastes like gold there!).

Regarding the cons, the fotovoltaic power doesn't have an environmental impact as bad as the dams. I guess the only one could be the visual impact. It even creates the possibiility to cultivate new cultures behind the solar pannels.

But, and there is always a but, there is much controversy about the solar power. The thing is that you can't store electricity, and as the production hours depend on the sunlight you will have a period of abundance and a period of scarcity that will not adjust very well. This will lead to an unbalanced match of supply and offer and so the efficiency of solar power is lower than other energies (a similar thing applies to wind power) like the hydropower where you can control when you want to generate it.

It makes me really proud to see so many good references to Portugal here in HN, for a country that is in such a bad shape it's good to see some things might change in the future.