Many long term users of Macvim like myself have been annoyed that fullscreen mode cuts off the first couple lines and shows a bar on the right when using OSX Yosemite. After trying out multiple forks that kind of fixed it but also introduced other problems I finally found a satisfactory fix. Just run this in the terminal to turn off yosemites fullscreen method on macvim.
$ defaults write org.vim.MacVim MMNativeFullScreen 0