OK, so I figure I ought to update this with what I actually found out.
I ended up trying
Microsoft Streets and Trips 2009, DeLorme Street Atlas 2009, Garmin MapSource+MobilePC (with both the CityNavigator North America 2010 and TOPO US 100k mapsets) and a couple of smaller, lesser know packages.
DeLorme Street Atlas 2009: Has easily the worst user-interface I've ever used in any mapping, navigation, or GIS program. It was knocked out of the running for that alone. However, it has a GREAT database of POIs, by far the best of any tested software. Sadly, the searching isn't as advanced as it needs to be. The in-route display is acceptably good, especially when the UMPC option is enabled. The mapping data seems pretty good, from what I saw. However, using it to manually find your way around an obstacle is almost impossible due to the HORRID UI.
Microsoft Streets and Trips 2009: Has a pretty good user-interface. It works 90% the way I'd expect and want it to. It has an OK database of travel-related POIs, but doesn't have SA2009's depth for strange POIs (
like the night I needed a coin-operated laundry). The generally good UI and generally good mapset allows you to work-around obstacles in real time fairly easily in the car. Sadly, the in-route display and voicing let the package down somewhat. In the end, this was a close 2nd, held back by the sub-par in-route display and speech.
Garmin Mapsource+Mobile PC: Has an ok, but not great, UI. It's definitely usable, but you have to be willing to work the way it wants and not the way that makes sense. The POI database in the CNNANT2010 maps is ok for most travel-related things, but that's about it. It's possible, but not quite as easy as it should be, to route yourself around obstacles in real time with this. The CNNANT2010 mapset has 90% of the roads I want to use, the Topo 100k 2008 map has the other 10%. Sadly, the Topo maps are not routable, causing a big PITA in the process. However, the in-route display is 90% of what I'd like and the voice prompts occur generally at useful times. In the end, this is the option that I chose.