This is an excerpt from a medical abstract I received today.  The article is short on details but affirms that penile rehabilitation does work.   
Division of Urology, The University of Texas Health Science Center at Houston
18 September 2008
“Post-prostatectomy erectile dysfunction affects a considerable number of men and is a significant quality of life issue. There has been a substantial amount of research on the treatment of post-prostatectomy ED, and now there is a rising interest in the concept of penile rehabilitation. The goal of penile rehabilitation is to moderate the destructive processes that occur after prostatectomy in order to preserve erectile function, either through spontaneous or assisted means.

“We reviewed published data and experiences of post-prostatectomy penile rehabilitation using regimented interventions of phosphodiesterase inhibitors, vacuum erectile device, and intracavernosal agents, and we present and analyze the research conducted.

“These studies show improved objective and subjective clinical outcomes in regards to physical parameters, sexual satisfaction, and rates of spontaneous erections.”

PubMed Abstract PMID:18784845