My ageing hand-me-down MacBook (late 2007 - 1GB RAM) has been serving me well - it ended it’s OS X life in the Autumn of last year and has been running Linux Mint 17 ever since - we call it the MintBook. Linux has been a saviour. Making the shift was easy enough (having used GNU/Linux before - mainly in Raspberry Pis and web servers), the ease of software development has been greatly improved (bar Xcode of course!) and it has basically resurrected an almost dead laptop.
Software Engineer based in New Zealand