If you import the GPX file produced by S&T2010 into RouteConverter version 1.29.17 or later, and then save the result as GPX version 1.1, you will overwrite the original file with the SAME data but with formatting added and the time correctly annotated as being Zulu time. Instead of 19:01:02-05.00 it will be 19:01:02.000Z. That is the way the standard for GPX wants the time shown... as Zulu or GMT. The time IS correct in the original file, but it is NOT -05:00 time, it is Z time. The formatting also makes the file easier to read, and it reads back into Streets and Trips just fine.
As for the other type of GPX file, which covers the start, stops and end of a trip, opening with Route Converter, checking each stop at maximum zoom in for that location, moving the stop to be more 'correct' and then exporting MAY result in Streets and Trips changing the route slightly. It has NO idea how to handle:
<wpt lon="-78.91968714229" lat="42.9078289320996">
<name>Peace Bridge Duty Free, Fort Erie ON L2A</name>
<type>Pushpin.gpx</type>
</wpt>
because the road to and from this Duty Free shop is not in their maps. Use this precise location and the route is crazy at that point of a trip across the bridge from Canada to the U.S. with a stop at the Duty Free. For that matter, the Canadian side duty free shops are not 'found' if you do a search for this type of business, but the U.S. side duty free IS found. [Another example of the data discriminating against Canadians?]
In any event, if you plan to export to a Garmin and want better precision, use Route Converter and make your corrections, then import back into Streets and Trips and export to Garmin or create a Garmin file right in Route Converter and export to Garmin that way.
An example of a factual data error from whomever supplies the original data:
<rtept lon="-107.22050607204437" lat="39.4129959852504">
<name>Days Inn-Carbondale</name>
</rtept>
is the accurate location for the Days Inn, in Carbondale, Colorado. Check in S&T2010 and it is found at
<rtept lon="-107.21728364937" lat="39.4115995801985">
<name>Days Inn-Carbondale</name>
</rtept>
which is about a third of a kilometer out of place <grin> so you might just want to make these sorts of correction <or not>.
In any case, I hope that the format supplied to the GPX file by Route Converter is followed by Microsoft for the Streets and Trips 2011 version of their GPX exports.