Shots are an alternative (I use Trimix once in a while), but pills, if you find a good option, sure beat vials and needles for logistics.
Read Mulhall's book, and go to Memorial Sloan-Kettering Cancer Center's site, where there are some videos of his presentations. I don't have the direct link at hand, someone else may see this and add it on.
My uro works through the "p's" - the pump, not so much for use in sex, but to keep the tissue stretched; the pills, on a daily routine; then the prick (shots).
The pump is not very useful for sex, but does at least stretch the tissues and keep plaque from building up in the corpus cavernosum according to some doctors. I was told to pump up, hold for a few seconds, then release a few times a day.
Pills vary. Levitra & Viagra are short-term. You take them at will. Cialis builds up in your system. The order from my uro is to use 5mg per day (because of insurance I buy the 20mg and cut them into quarters as best I can), with a 20 taken once in a while to see what additional reaction I might get. He also loaded me up with samples of the others, but none did much except give me blue vision. Have a talk with your uro or GP about the pills, but Mulhall would have most of us on a daily routine right out of surgery.
For me the Trimix is a guaranteed result, maybe too much. I like to think it works so well in part because I have stayed with the routine.
Getting a Trimix prescription is not too hard, but finding a compounding pharmacy and getting any assistance from insurance are complications. You will most likely be told to come in to do the first injection at the uro's office for training.