What can I say beyond "I love this program". ESRI should take a hard look at the program and be afraid. In my opinion, this is a harbinger of GIS programs to come: it's intuitive, powerful, and flexible. It also is stable and relatively inexpensive. It will read virtually all commonly (and some not so commonly) used GIS vector and raster data formats and translate among them (I call it the Rosetta Stone of GIS). It also does effortless on-the-fly reading of projection information and reprojection. It also can digitize data, add new ASCII data, merge datasets, etc., etc. I now use Global Mapper for most early data acquisition and save ArcMap for later refinement of the data.
The program is not really intended to produce finished maps although it can do a fairly decent job on some. It started out as a simple viewer for dlg's produced by the USGS. It has developed into much more but more expensive and cumbersome programs must be used for producing a professional-looking finished product.
The help manual is online, quite well written, and succinct. I you familiarize yourself with the toolbar, that's probably most of what you'll need to know.