Honestly, I haven't really figured out how to use Global Mapper yet. I've done GeoTiffs with Dem2Topo quite a bit, but my first real experience with Global Mapper was trying to follow the tutorials. I'm waiting to read the remaining unwritten articles to understand what to do with the files that Global Mapper created. I couldn't find a way to export as shapefiles or anything that I'm already familiar with, it was all grayed out. There's a step I'm missing and don't quite understand yet I guess.
At the moment, I've got the whole state of Maine (10-meter I believe) in ArcGrid format and I've got Penobscot County in GeoTiff. I'll probably finish my county the way I'm already familiar with using Dem2Topo, OpenStreetMap, etc. I'd like to see how Oz is doing some of the other cool stuff though like railroad tracks, power lines, etc. This should be a pretty sweet site when all the tutorials get finished.