Well, I've been very happy with my 2009 macbook white C2D 2.13, until recent need to run some heavy processes like Virtual Machines and heavy compilations... memory upgrade to 4GB helped a little, but it still lacked CPU power. So I eventually bought MBP 2012 "13 for that. I still like the feel and design of my white more than aluminium body... but that's another story... Anyway, I plan to give the white to my daughter. It currently runs Snow Leopard and I wonder if I should upgrade to Mountain Lion? If I was using the white, I'd stay with SL for sure. But my daughter would most likely appreciate extra fanciness of ML... So I'm thinking of upgrading to ML unless this imposes some noticeable performance degradation. So, my question to those of you who upgraded... how is it?