Epocrates Rx iPhone appears to work. Initial impressions are that it's a large improvement over ePocrates on the Pearl, and in terms of utility it's probably comparable to ePocrates Palm.
The med images are particularly impressive.
The only downside is I think it's getting more obnoxious about insisting I glance at the marketing material that pays for the service. I hope they're not running into funding problems -- that's usually what makes ad-funded vendors push the marketing.
My iPhone 2.0 impressions so far is that synchronization with Outlook or MobileMe is a disaster, Outlook sync is a regression from iPhone 1.0, and basic PIM (calendar, etc) functionality scores a D-. Everything else is pretty good.