warts

Plugins typically map your keys without asking you to init them. In addition, they might map them in all modes even if inappropriate. Good luck if you defined your own.
- e.g. swap_parameters.vim maps gs, gS, gb, gB unconditionally in all modes.
Can't nest ":redir". There's only one level. You can't even find out where stuff is currently getting redirected to. So pretty much useless in library code since something you call could reset it or you could be resetting the user's redir.
Ugh ... there are so many. I'm not switching. Learn to live with it!