Not that much to be honest, there are some quirks and such as variable scopings (g:, s:, l: a:) and other things, but other than that it's pretty familiar.

A few great resources I found after having googled a ton around was [0] and [1]. If you are very familiar with vim (I'm not really a power user tbh), then all the commands you use with : are supported in vim script. Meaning opening a split in your script is, well, just split.

[0] http://ricostacruz.com/cheatsheets/vimscript.html

[1] http://www.ibm.com/developerworks/library/l-vim-script-1/