I'm an engineer and can't help think of cost effectiveness and trade offs when faced with multiple ways of accomplishing a task. When you are talking science return, there is no comparison between manned efforts and robotic. Robotic efforts have been returning 100's of fold of science return for the money vs manned efforts.

If a space station had been designed for robotic control of science experiments instead of supporting manned presence, we could've already performed literally orders of magnitudes more experiments on the ISS than has currently happened.

Until we reduce cost to orbit tremendously, significant manned presence doesn't make much sense. Such manned presence can only be justified currently if it is supported through tourism or entertainment media for the novelty factor.

Even one of the few legitimate areas of manned space research (sub earth gravity effects on humans), would have advanced much farther by extensive animal studies as an alternative to the overwhelming cost of sending humans. In space we can create artificial gravity if needed, so the key datapoints would be gravitational effects of Mars and Moon gravity, which we could simulate on a space station.

I am not against manned presence in space. To the contrary, I think it is our destiny and in a few centuries, there will be untold billions living in artificial structures around our sun and planets. However, the quickest way to get from A to B, is to do things that are technologically sound, and cost effective. These things pay back and you can reinvest the returns to get to the next step.

Until we develop something like the space elevator, that reduces the cost to access space, manned presence should take a back seat to robotic and telerobotic exploration. I'm more interested in the science than government subsidized joy rides.

If manned space flight makes any sense(is profitable), the commercial sector is the one to handle it. They will not generate technologies without business plans that have some connection to long term accountability. Once a commercial enterprise can find an appropriate model to actually make money off of manned space flight, it will rapidly advance. They will feed back their profits to develop ever better and more sophisticated services. (See aviation industry.)