Re: gps maps
Most HBs come with Unimap, which is just a basic map. For most inland water, it is just the outline of the lake,etc. For 2010 they are adding ContourXD, but not sure what that is, but think it will be the basic Navionics Hotmaps for selected lakes, just built-in to the unit. HB supports Navionics chips, navigation and lake contour fishing maps. Also in 2010, they are adding support for LakeMaster chips. Unfortunatly, these are only available for selected areas/states.
Side Imaging is a whole other thing. I like it for finding structure and how it is laid out. It's great for fishing new water. Lowarance's version is now out, but from what I have heard, finding it is hard. It requires adding a new transducer and module to HDS units.