The application is capable of processing GPX, KML, TCX, FIT, IGC, NMEA and Garmin CSV files. Open various types of GPS log files and use both online and offline maps GPXSee certainly seems to fit the bill, as it supports multiple popular GPS file formats and comes with some attractive features, all packed into an intuitive, modern GUI.
A straightforward tool that can help you view and analyze GPS log files is likely to come in handy, but you may have a hard time finding a user-friendly application that offers a strong enough feature set.