It might be worth taking a look at ArcGIS Explorer(free at esri.com). It's got a better topo series (better trail and location names) and the same satellite imagery. It's got higher processor and video card demands, so difficult to impossible on older computers. It does both 2D and 3D; does nice "fly" stuff and handles all the major geographic projections (dd, dms, UTM, grid etc). A fair number of tools and AddIns are being developed. That said, I don't think it's quite as intuitive/easy to use as Google Earth or Maps, though I now prefer it.
g.
