My 5520 has been flawless and is also just over 2 years old. I have the 1080p matte screen though. Only other laptop I had that has come as close to nirvana as the 5520 was a Thinkpad T42 and 2012 mbp 15.
dead battery might have been my fault, I opened up the laptop to take a look at the hinge and may have shorted something...I think I used a screwdriver or metal tool to push in the connections when reassembling
