As far as I know only Garmin mapsource maps can be loaded into a Garmin GPSr.
I have Mapsource topo maps in my Garmin Vista but download tracklogs and waypoints on my pc into N.G. TOPO! which has 7.5 maps. Then if I want to print out maps etc... Its quite detailed.
No, the detail on the Mapsource CDs is "ok," if you don't go too far from your vehicle. The only reason I don't like the Mapsource CDs is I would like the detail to be the same as a 7.5 minute map. I hunt in the San Pedro Wilderness Area of the Rockies and I need serious detail, not 1/100,000 detail level. The level of detail the Mapsource CDs provide is the same as a BLM map.