Paul Spudis gave his views, positive and negative, on NASA's implementation of President Bush's Vision for Space Exploration at the ISDC 2007. Here is a simplification:
- RL-10 engine can use in-situ lunar propellant
- Building an Outpost on the lunar south pole
- Lack of Robot Probes
- Lunar orbit rendezvous instead of an Earth-Moon L1
But the biggest complaint was that NASA's lack of a single complete mission.