My statement may have been over-interpreted.
I have seen many posters who comment that the meds (meaning Cialis, Viagra, and Levitra) help, but that most now need a bit of extra stimulation. Thus my comment that you should not expect a pill to cause a spontaneous woody. I hope that I am wrong, but approach it with reasonable expectations.
The shots act differently, and may.
Taking the meds early on is to get circulation moving, and as Steve said, some of us take them for primarily that reason.