Re: completing-read in E21

[Richard Stallman]

    For example, I want to visit the buffer containing the file `thisfile.c'
    and start typing `C-x b thisf' when ido-switch-buffer reports "No Match"
    because I haven't opened the file yet.  So I just hit C-f which brings
    me into ido-find-file with `thisf' as the initial input (usually allowing
    me to just hit RET to open the file).

    For this purpose, it is necessary to be able to fill the minibuffer
    with initial input!

I don't think it is necessary.  You can let the user type M-n to pull
the default into the minibuffer.  Why do you think saving that one
keystroke is so important?