As I've mentioned to a few people offline, there's going to be an IEEE paper discussing the mission that will be presented in about two weeks at their aerospace conference. Jeff Foust was able to dig that out and get a copy, and provides some details here:
http://www.newspacejournal.com/2013/02/21/new-insights-on-that-private-crewed-mars-mission/Key points (that I feel ok sharing since Jeff made them public):
* Two person mission
* Free-return trajectory that flies by Mars
* Launched on a Falcon Heavy
* Modified Dragon spacecraft
* Privately funded, but leveraging NASA expertise in a few key technical areas (TPS and ECLSS)
While I'm not a manned spacecraft guru by any stretch of the imagination, my read of the paper left me feeling pretty confident that the idea was technically feasible (ambitious? yes. balsy? yes. aggressive mass targets? yes. achievable? probably.)
~Jon