I bought a Lenovo which broke 2 times within the first 6 months, all under the one year warranty. One of the guys in Lenovo told me that it was my fault for not buying a top of the line unit and only getting the "cheaper" thinkpad. They blamed me for the damage and wanted to charge me 400 to fix a $600 computer within my warranty. I kept calling and they passed me around from person to person and was running around in circles. I called AMEX and they cancelled the charge after ruling in my favor. AMEX was so great to deal with.
Then theres a non Amex part of the story. 1 year later, Lenovo sent a collection agency after me for the purchase price of the computer. This really set me off. I took the AMEX judgement and filed a complaint with the NY Attorney General's office. That got the attention of their higher ups. One of them contacted me so I told him to call off the collection and I never wanted to hear from them again, and that was it.
I learned that AMEX is very helpful in disputing charges on faulty merchandise, and Lenovo is faulty merchandise with terrible customer service.