Search & replace using quickfix list in Vim

Question

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

Answer 1

nelstrom's answer is quite comprehensive and reflects his brilliant contributions to vimdom. It also goes a bit beyond what is strictly needed here; the quickfix step can be omitted in favor of populating args with the result of a shell command:

:args `git grep -l findme`
:argdo %s/findme/replacement/gc
:argdo update

should be all you need.

Edit: as Domon notes, :set hidden must be done first if it's not already set!