Thanks, Mark.
For anybody else's interest, I've noticed a couple of things. Suunto's Movescount allows downloading of the expected file formats for activities, but not the Suunto proprietary XML file format, SML (Suunto Markup Language). The files available (TCX, GPX, etc.) get imported into GC with some serious discrepancies that make them unusable. However, it turns out that when Suunto activities are imported directly into SportTracks from a SportTracks Suunto import plugin, an SML gets dropped onto the hard drive. And THIS SML file imports wonderfully into GC.
For the record, I'm investigating this area because my wife is a runner who uses a Suunto Ambit 2 and has used SportTracks for many years. I'm wanting to get her running historical data into GC to start playing around with it.