My understanding is that 50% of your Medicare visits have to have a e-prescribing code - their are 3 different codes - 1 is that all scrips were sent electronically (not faxed), 1 is that for some reason you did not send all electronically (pt/pharmacy preference, controlled substance, whatever) and the the last 1 being that all scrips were sent electronically. It is a G code that you send with your bill to Medicare.
Ironically - the mail order companies do not let you do them electronically as far as I can tell. This is because although some companies provide e prescribing to you for free - they charge a fee to the pharmacy to get them. One neat thing about e-prescribing is that it automatically finds out their Part D company and gives you formulary feedback (not perfect, but is getting better).
The current e-prescribing from AC does need improving and I know that Jon was working on it, but had to focus on Version 5 due to CCHIT certifcation. Once that is done I think he will get back on his other priorities. I currently do the e prescribing even though it is clunky, just to get up to speed (only on medicare - don't want to financially burden my small town pharmacies too much yet).