I just purchased Geojournal as well - the last technology piece I need to get started with geocaching.
It uses exactly the same waypoint files from geocaching.com as I use for iGeocacher (the iPhone application that I use for carrying Geocache information with me.
And what a enjoyable application it is.
After downloading files from geocaching.com to my webserver (as described for iGeocacher) both applications can get hold of the files, and this is what it looks like in Geojournal (after I have told it the location of where I am at the moment)

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