So far I always used EasyGrep for replacing text in multiple files. Unfortunately it is quite slow when a project gets bigger. One thing that seems to be amazingly fast is G
There's a patch to add the cdo (Quickfix do) command to vim, but it has not been pulled yet (as of 2015-03-25):
https://groups.google.com/forum/#!topic/vim_dev/dfyt-G6SMec
You may want to patch vim yourself to get this patch:
brew install hg # install mercurial, e.g. with homebrew
hg clone https://vim.googlecode.com/hg/ vim
cd vim
# copy/download patch to . folder
patch -b -p1 < cdo.diff
./configure
make && make install