Ive been using the Epocrates app since the first day it was available for use. It was free at the very beginning. I know I had it on my Palm Treo. Later I more than happily paid for it--I used it every day in my exam room and office. Now as a retired physician who does some volunteering, the free version is enough for me. Still offers lots of information.
ArtAsArt about epocrates, v16.8.1