I'm really excited about the prospects of this project and for the future. I've seen some hype for what we could potentially do on mars and the big one is colonization and/or simply manned trips.
Personally, I'm of the opinion that we'll never see colonization of mars on any real scale. What I can see us doing, however, is harvesting the resources of mars and bringing them back to earth (this is obviously a long ways out and not any time soon). Perhaps a space station orbiting mars with some mining in safe areas and small, hardened shelters for humans to live in when they're working on the surface.
Since mars has a thinner atmosphere than earth it's much more prone to all kinds of space debris crashing into the planet, which would be detrimental to any kind of structures we have on the surface (and that of human life). As Nasa stated in their video, there's just enough atmosphere to slow an object down, but it's just not enough - many will still get through, as evidenced by the surface of the planet.
Next, the weather patterns and storms. From what I can see there's some really nasty storms on the planet and there's no telling what kind of adverse affects they would have on people and objects if they're caught in them. With all that red sand flying about, it would be hard to keep it out of anything mechanical too and so a lot of things would probably break down without constant maintenance.
Just some random thoughts based on what I know of Mars. I'm of course not a scientist and I could potentially be wrong, but I just don't see us ever just up and moving to mars - compared to earth, it would be pretty much suicide for us to go there. If we fuck up this planet we're screwed.