Sorry, I missed the question about the maps in S&T. They are about as good as you can get for North America; better - eg. more up to date and complete - in highly populated urban parts of the country and less so in more rural and lower populated regions. Microsoft and Garmin both use map data from Navteq. I have S&T 2008 and Garmin's City Navigator v8 and 2009. The Garmin v8 is a year older than the S&T2008 map data and 2009 is a year newer. There is virtually no difference among the three of them in the rural regions. In the large urban centres you see the additions you would expect to see, year over year, from new construction in those areas.
The only caution is that the map data is typically at least two years old by the time Navteq assembles the data and the major vendors like Microsoft and Garmin are able to package it, test it and roll it out as a complete product. So my Garmin City Navigator 2009, which is about the most up to date product on the market, has, at best, 1st quarter 2007 data in it.
Related to your issue of poor location display of the vehicle icon on the map versus where you really are, there are only two things that will cause that. One is poor accuracy of the GPS signals so that the nav program is having difficulty placing the indicator in an accurate position on the display.
The other is poor calibration of the map data itself. I have not experienced any calibration issues with Navteq's map data and I have been using the Garmin maps based on Navteq data since 2003. If I have a good enough signal for accurate calculation of my location on the face of the planet, it will be displayed equally accurately on the map with either Streets&Trips or the Garmin products I own.
To support that you need only look at the pickle Google Maps has created for themselves by dropping Navteq for North American data and going with TeleAtlas. TeleAtlas has always had questionable data for North America and you can see it in all of its glory on Google Maps now. Their forums are overloaded with complaints.
I'll shut up now that I've probably made your eyes glaze over with more details than you ever wanted to know.
...ken...