When I was at the AIAA meeting in Pasadena last month, Doug Stanley told me that this study would be coming out soon:

Commercial launch with propellant depot architectures significantly improves the extensibility and mission payload capability by providing a robust framework for all foreseen missions in the next 30 years. Adding to commercial launches every few months provides experienced and focused workforce to improve safety, operational learning for reduced costs and higher launch reliability, reduce launch costs depending on the government/industry business model. The depot framework allows multiple competitors for propellant delivery that is low-risk, hands-off way for international partners to contribute because it is not in the critical “mission” path and provides redundant alternatives available if critical launch failure occurs. The architecture provides reduced critical path mission complexity (Automated Rendezvous and Docking events, number of unique elements), provides additional mission flexibility by variable propellant load. Commonality with COTS/commercial/DoD vehicles will allow sharing of fixed costs between programs and “right-sized” vehicle for ISS, thus stimulate US and international commercial launch industry. Development risk is reduced by eliminating four space elements including the major Earth-to-orbit launch vehicle and solar electric propulsion transfer vehicle, large mass margins with current and proposed launch systems, and the Cryogenic Propellant Storage and Transfer in-space technology demonstration program. Finally, the architecture creates powerful partners from commercial US industry and internationals that increases political sustainability of the overall program.

But other than that, it totally sucks.