I am looking forward to this being a default feature. Glad to hear it made it in.
I constantly use it on my sites where we (as a team) edit documentation and what not.
Having an inline editor helps us organize the data in front of us, and the ability to scroll up and down and go back to the editor and continue editing.
What I especially like about inline editors, they've got the full width of the post, so it's more accurate as to how it looks.
Be patient and be happy with what you've got now . I mean, this is a beta of version 1. That is: o.n.e. This whole version 1 already beats every other single forum package out there when it comes to the UI/UX (which is of an essential importance... something other packages such as vBulletin and even Invision still don't seem to grasp). And when it comes to functionality (Invision and vBulletin offer more then XenForo) I am sure that much requested/needed features will see the light of day sooner or later in XenForo.