two years after getting my 360 core system, I had the RROD. Bought a 20 dollar ebay fix-it kit and it has been perfect ever since. My kids now use it to play. Never had YLOD on my 60GB phat before I sold it, and now my current slim is perfect.
Yeah I was lucky because I had my 360 under the old Best Buy warranty plan where you could just exchange it for a new one. I has 2 RROD and one E74 error. All were exchanged under that warranty. Sadly BB doesn't do that anymore. My PS3 was under Gamestops warranty so I was lucky there too.