360s are cured of the RROD issue. 3 year extended warranty guarantees the 360 will have very few issues. Re-designs of the 360 models over the last few years have increased the reliability of 360 consoles. New models of 360 do not overheat as much the launch models. 360s have better chips in them and require less energy to power them.
360 hardware reliability is now on par with the Wii and PS3 which only have 1 or 2% failure rates. There will always be a lemon in every 100 things sold. That is life, nothing is perfect.