I had my last IMRT/IGRT session about eight months ago. I had only minor urinary and bowel problems for about a week in the middle of the 45 sessions. I have had no urinary nor bowel problems since that time.
On the issue of erections I am not sure. I am on hormones and really have about zero sex drive. I am also single with no partner at this time. I have had some spontaneous erections in the morning and yes they were good enough for sex. However, my oncologist has said that I would probably lose the ability to have erections as time goes on. The literature says about a 50/50 chance on regaining potency after radiation.
In general the radiation treatment was fairly benign. I have had more side effects from the ADT than the radiation and they will continue until the hormone is stopped a year from now.
Good luck with your treatment regardless of what you choose.