"A study done by Bruce Tognazinni when we was at Apple (a company that has had a good track record of designing for the mouse) showed that using the keyboard felt faster but was slower while using the mouse felt slower but was actually faster."
And it will almost certainly always be easier to do actually complex operations via text (especially if you might be repeating them or slightly modifying them). Just yesterday I was generating a PDF packet with pdftk, and had a command line of the form "pdftk file1.pdf file2.pdf blank.pdf file3.pdf cat output outfile.pdf" that I kept having to re-run (because I'd modified file2.pdf) or tweak (because I added file4.pdf). It's possible that the first pdftk would have been quicker in a GUI---though I'm not convinced---but in the aggregate there's no way a series of GUI ops would have been faster. And I'm not even sure how I'd accomplish something like "mv *.jpg jpg_subdir/" in something like Finder without a lot of manual finding and clicking and dragging and making mistakes.