An excellent point; having a command line in your editor is something whose value is hard to recognize until you've tried it, and hard to overstate once you're used to it.
It might, though, be worth using the typical Emacs nomenclature for key sequences, i.e. M-x where you use 'MX' and (assuming your Command key is bound to Meta, as is ordinary for OS X Emacs users) M-. where you use 'CMD-.' -- your choice of preferred nomenclature is of course up to you, but using the standard forms makes it easier for other users, particularly neophytes such as the one to whom your advice here is directed, to understand what you're describing and relate it to the Emacs manual and to whatever other resources they're using.
I changed this because I found M-x to be really really difficult to type. It may be my hands or my fingers, but I have a hard time doing that key sequence correctly. Apart from that I think that you're absolutely right. I shouldn't have advertised this as it will probably confuse users.
Well, there's nothing wrong with rebinding M-x; that key combination requires a lot of hand scrunching, which can get uncomfortable after a while. Nothing wrong with talking about it, either! I'd just recommend describing it in accord with the conventions for Emacs key sequences, is all.
It might, though, be worth using the typical Emacs nomenclature for key sequences, i.e. M-x where you use 'MX' and (assuming your Command key is bound to Meta, as is ordinary for OS X Emacs users) M-. where you use 'CMD-.' -- your choice of preferred nomenclature is of course up to you, but using the standard forms makes it easier for other users, particularly neophytes such as the one to whom your advice here is directed, to understand what you're describing and relate it to the Emacs manual and to whatever other resources they're using.