You picked the simplest refactoring, for converting local to instance variable I agree with you, this is easy in Vim.

But still there are some potential problems:

1. The variable already exists in the class. 2. You accidently mark to much or to few lines with ":<,>%"

For refactorings such as extract method the number of preconditions and information to gather is much bigger, such as input and output variables, existance of return statement etc.

We plan to integrate the tool into vim as well, so that you can call the refactorings through vim directly.