Changes are almost entirely cosmetic. There is one slightly misprinted card in the first edition. The resource bits are smaller overall, which is good, in my opinion because they're all more the same size. The box is different color (I like the newer one better.)
But like, unless you're seeing someone sell their first edition cheap for some reason, there's no reason to worry about-- only the second edition should really be in circulation right now.
Great, thanks. By the way, how do I know if my copy is first or second edition. I see some box art where the title has a light coloured background while mine has a dark maroon background. Also, my copy doesn't have the '2014 spiel de jahres' winner stamp. Is my copy first edition?