Kim hits the main point of it. Cross dressing is a sufficiently socially inconvenient if not outwardly proscribed behavior that I think few of us would engage in it if it weren't for a strong inner drive. That inner drive, regardless of whether it is toward transition or not is sufficient to align us within the Transgender spectrum.
If any one on this board is a trans person looking down their nose at cross dressers or a cross dresser looking down their nose at trans people, please STOP IT! In our unity and our loving respect for each other lies our strength.