Having also come from CoH/CoV I am used to the idea of having multiple builds. They made sense within that game's framework, though. In WoW I dual-spec'd a Paladin but it was for very off-moment times. In the end, to me, I am in favor of choice--and like the OP said especially later as this game matures and we all (including Bioware) have more experience with SWTOR gameplay.
While I understand the fellow who suggested a driving metaphor for playing different classes I also do "get accustomed" to playing any individual character a certain way. I'm not averse to suggesting to a team that I could fill in a needed gap but I am averse to teams demanding players change rolls (in general). When the team is used to playing together, however, it's just a matter of communication and team planning.
So, after a year this thread should have even deeper insights. In the end if Bioware implements dual-spec they will probably have lots of game mechanics in mind. I'm all for player choice. Whether I chose to dual-spec will depend on whether it's useful for me, however.