I use it as a 'run through' for exported GPX files from sites like Mapmyride so that Garmin Connect will allow them to 'manual upload' successfully.
The manual upload problem is due to the fact that some sites do not save the data quite how Garmin Connect needs it, however
www.gpsies.com will convert their data to what Garmin Connect will accept for the manual upload. So, via their 'Convert' page you 'choose' the '.gpx' file you've exported and saved from another site, select 'convert' to a 'GPX Track', when converted this will then load into Garmin Connect; note it uploads it as an 'Activity' that you then save as a 'Course'; so don't forget to delete the 'Activity' afterwards so they don't count towards your total.
Paul