Let's just get this out in the open: I think we should colonize other worlds, and I think we should do it yesterday. There is no greater aspiration that I have than to facilitate the beginning of a diaspora of the human race to the rest of the solar system, and even (or especially) beyond. Perhaps "trickle" would be a better word than diaspora, though, to begin with.
And that's all I feel I need to say about that, if all that stood in the way was the engineering.
Except that there are so many other things that go into such a feat. Some things I can think of off the top of my head are education, politics (unfortunately), and public interest.