I bought a 27 inch iMac that I must constantly send to repairs. How do I get my money back?

Question

I bought this imac at the end of last year.
After 3 months the screen started to get smudges all over the place, and since I work in video production, thats just something I cannot have.
I sent my computer to get repaired, and they replaced the screen. It's been 2 months, the screen is getting burned again, and now it crashes constantly, I get the "white screen of death", it doesnt boot up, then the screen starts to flickr like a strobe light. I try again, and then the screen turns all blue, like a blue screen you get using a windows based PC. Now I luckly managed to boot it up, and came straight here, and if I manage to finish this post without it crashing again its a great deal of luck.
I called the apple call centre, and they said that apple somehow managed to replace my screen with another defected one (yes, they actually told me that) AND that I probably also have a defected seagate hard drive that they are replacing in all the imacs bought from 2009 to 2012. They also said that its "weird" that they didnt replace it the first time it went to repairs.
I do all my work on this computer, and I can't manage to constantly be without it to send it to repairs, and that is probably whats going to happen, till my warranty voids, then I will be the proud new owner of a 27 inch brick.
Im extremely dissapointed at apple. I was willing to pay 2000 euros for a computer, because then I would "pay for quality" of the product, and get good service. Well the product obviously has severe problems, and the customer service is even worst. They told me all that ridiculous stuff that puts apple in a shameful position, and also shoved me aside to deal with my problem with someone else. They said the only way I could "try" and get my problem fixed, Is if I send an actual letter (because apparently people still do that) to the Apple Europe Headquarters in Ireland. I live in Portugal.
Before the apple europe headquartes in Ireland ask me to send a pigeon to the United States, I would like to say that i'm probably never going to buy products from Apple ever again. I'm not the only person with this problem, and people close to me are having exactly the same problems and feelings twords apple. If I get my money back, maybe I will still buy my music from iTunes, that at least hasn't given me any problems...yet..

Answer 1

I have some news on my situation, and some news on the problem of the screen itself.
First, this still could be wrong, but here is a possible explanation for the screen problem:
http://www.hardmac.com/news/2011/04/05/investigation-of-the-marks-on-the-imac-sc reen
It seems that the mac is overly sensitive to dust, but the only dust that actually goes in, is a very thin kind that you have pretty much everywhere. Maybe the heat from the computer makes the dust stick or something, I don't know.
Anyway, I wen't to the store where I purchased my 27'' imac, and asked to talk to the manager (it's one of those big chain stores, like best buy, but in this case its called "Fnac"). Apparently I was terrebly missinformed by pretty much everyone, including "Fnac" employees. It appears that I am in fact protected by portuguese law, and everytime I get a new component replaced, I get a new 2 year warranty for it (in Europe you always get 2 year warranty for everything, instead of 1). And, after the 3rd attempt to fix a recurring problem, I can in fact demand the money back, or a replacemement new product. There is still some glitchy stuff on that matter though. The manager said there is this problem in pretty much in every retailer everywhere - there are 2 kinds of stores that sell apple products: there are those stores that are just intermidiates between apple itself and the customer, witch means that for every product they sell, they only own a small percentage of it; and there are those who buy apple products, to resell them to their costumers. On this second kind of stores (like Fnac, and probably BestBuy and such), where they resell, they have to give you the money back because the law says so (since they own the products they sell). But Apple on the other hand doesn't allow it. So basicly, they have to give me the money back or a new product first, and then ask apple for permission and hope for the best, because if they dont give permission, the store will loose the money the product is worth.
My problem is "kind of" solved though. Now I know that even in the worst case scenario, I can keep replacing the screens once or twice a year, witch is not really great because I'll not be able to work on it for around 2 months in every year. It's still bad for apple, and its sad that the ones who actually solved my problem was the europe consumer laws, the portuguese government, and the store. Apple, a company that at this moment makes more money then the united states, doesn't have a solution for me, and doesn't agree with the solutions the other ones gave me.
Thanks for all your help and opinions. They gave me some perspective.
I will still be on the lookout for more answers, and if anyone has the same problem I can use my experience to help them.