It can really help when I'm trying to get a sense of a website's structure. The Content Map tab reveals a map in Gather, but once you have more than say, five or ten items, the map display isn't really usable. (It stretches too wide - can't be viewed on a screen).

I end up going to slickplan (slickplan.com), where my company has a free/cheap account. I reinput the IA so I can see a more manageable view of my content map. Slickplan's not perfect either, but it lets me see a whole lot more, which then enables me to take real advantage of drag and drop features.