When I installed v10.11 the installer crashed and I could not do anything. I took my MacBook Air to Apple Support and they only solved the problem by formatting the disk. This costed me about 80 Euros, not to mention the 2 days without computer (it is the computer of my work), and the next days trying to setup everything again. Can I somehow reclaim these money from Apple? Definitely it was not my fault the installation error, and they seem to recognize it with this update...
MacBook Air, OS X El Capitan (10.11.1)