So you haven't had any issues but are worried because other people have had issues? Just use the thing and enjoy it, no need to be paranoid over something that may never happen.
Generally yes, if the class actions are successful then it will prove in a court of law that the machines are defective, and Apple will need to correct these faults. If however they are unsuccessful then likely nothing will ever happen, as it will stand as a benchmark that they've proved nothing is wrong. I wouldn't read too much into there being three though, these are big money payouts for law firms, and they all jump on them. Basically just sign as many people up as possible and it adds to the court fees the defendant would be required to pay.
However, as this is not a worldwide court, it would only apply in the country of origin. Although likely a similar class action would occur in other areas if successful.
For future though just buy the Apple Care with them, it's not much but it's worth it. I've heard people being upset that it's needed repairs but thankful they had AC, which is basically like winning a gamble so all good. Covers you for three years, most people buy these as work machines so three years is a good time to replace it anyway. Problem solved.