Well, I just did this myself, had exported/imported my iTunes library using some guides I found via Google meaning most of my apps were already present on the Mac. Just syncing now and it came up with the option to "merge information" which I think is the contacts etc, with the Mac or overwrite with the ones on the iPhone, I chose "merge" of course! When syncing my apps it said that I could either overwrite the iPhone or authorise the Mac with my iTunes login (which I did) and copy the apps across, going well so far, will let you know when it's done.