I don't have an iPhone, so can't say. But, I use BeerSmith 2.0 in conjunction with Dropbox to sync it between my PC and Mac. The trick is that you copy all of the files for Beersmith from its folder and put them into a folder in your Dropbox folder. Then in Beersmith, you change your working directory (it's easy) so that you're working from that Dropbox folder. Dropbox syncs that folder across whatever computers you set it up on.
I suppose it's the same as working off of a network folder though. But, the difference is you wouldn't have to have the computer hosting that network folder turned on if you're using the other computer.
The *only* problem I've seen is that the beer recipe view for printing out doesn't work. It doesn't show the ingredients. But Brad the guy at Beersmith is aware of this now and guessing he'll fix that.
HOMEBREWING SINCE 1997