see http://www.geophys.washington.edu/Space/SpaceModel/M2P2/

M2P2 is a developmental technology at a very early stage, which is why research is being funded by NIAC (NASA's Institude for Advanced Concepts; a group with a stated brief only to look at technologies in the 10-40 year development period range). Potentially it's a very powerful tool, with many of the adavntages of solar sails & few of the problems (although the top speed of a M2P2 driven probe is much lower than that achievable by sails); & all of the research done under the NIAC contract - which ends this year - seems to suggest that the system can actually be made to work; but that's a long way from saying that the system actually WILL work in the real universe.

There are two major problems: generating plasma fields in the multi km range needed to create significant thrust & not frying the circuitry of any probe you're carrying in the process. At the end of the NIAC contract - & assuming that all the lab tests continue to prove positive - a simple test deployment of a M2P2 plasma sail (ie, to prove that the basic inflation system works) using a small booster & Star SRB would be a very valuable New Millenium-type test flight; but unless you were looking at flying large numbers of high delta v missions immediately, its unlikely whether the technology at its current level is really worth the hype NASA originally gave it... like solar electric propulsion, even a fully functional M2P2 won't help you fly easy missions any cheaper, it will only make a lot of expensive missions (multibody orbiters; heliopause explorers; etc) a bit more feasible....

Robert