Based on our experience the people who take appropriate action are far outnumbered by those who have every good reason to complain.
There is no doubt that the Spanish legal system is very slow and expensive and unreliable but it can be made to work as evidenced by this latest court ruling. And certainly when your property is the subject of court proceedings that could result in the demolition of your home you either get involved or keep your fingers crossed and hope for the best.
If you do consider taking action you need to have realistic expectations, engage a lawyer that tells you what you need to know, not what you want to hear and expect that it will cost you money.
And if you cannot afford the cost of a lawyer it is worth considering making your complaint in positive ways which do not cost a lot of money and can only help. It is probably fair to say that your local Collegio de Abogados and FACUA ( the Consumer Protection Association) are not indundated with letters of complaint. Write in English if you must but write all the same.
As for our small group of homeowners .... we haven't quite figured out the key to success yet but we are pretty certain that the key to failure is giving up!