The two main issues for me are failure rates and key travel. My fingers literally hurt when I use it. The 2012-2015 form was probably less beautiful to look at (and slightly thicker), but it was much better to type with.
I'm glad someone else mentioned their fingers physically hurting when using it. I haven't seen many other complaints round this online and its shocking - This made me stop using the device completely - I was in pain just by typing normally!
