Perhaps I'm just not seeing something right in front of my nose (something I do often) but I can't see any mention in the beta book that when you maintain a grapple, that you must (or can) enter the opponent's square. The description indicates that the opponent must be in an adjacent square to grapple. I am guessing that sharing a square while grappling has been tossed from the rules?
Are there any rules for entering an opponent's square while grappling now? Even the pin maneuver doesn't indicate if you do this.
If I have read the rules right though, I do like how it mentions that you move the oppoenent to an adjacent square on a successful grapple. That would be quite useful (and logical) for large sized grapplers.