Scientists have a wide range of attitudes toward human spaceflight. Some think it incompatible with, even inimical to, scientific goals. Others think the two not only compatible but essentially the same thing—for them, curiosity-driven science and because-it’s-there exploration are two sides of the same exploratory urge. Others think that humans will eventually want to leave the planet, out of either desire or desperation, even if the time has not yet come.
Whatever their views, researchers agree on several basic points. First, although astronauts can conduct useful science in space and on the moon and Mars, the cost of sending people greatly outweighs the scientific benefit. That may change in the future, as robots reach their limits, but for now a human program must be decided on its other merits; it is not primarily a scientific project. NASA administrator Michael Griffin has said explicitly that the moon/Mars initiative is not about science, although science gains by piggybacking on it.
Second, the space agency needs to respect the firewall between robotic missions and human missions, because the goals of these two wings of the space program are, for now, so distinct. Third, government initiatives and private flight each have something to contribute. With the retirement of the shuttle and then the International Space Station, Earth orbit can increasingly be left to the private sector, freeing NASA and other agencies to stay at the cutting edge.
Finally, if the nations of the world do send astronauts into space, they should at least give the travelers something worthy and inspiring to do. For most researchers, the space station, at least in its present form, does not count. Mars does. The moon is still hotly debated.