agus,
GPS is approved for BRNAV (area nav) ops in most airspace,in fact its a requirment for most commercial operators as most routes these days consist of waypoints (points in space) rather than VOR to VOR navigation,although most of these waypoints are originally based on VOR/NDB radials etc it would be impractical to navigate this way in todays busy airspace,ie a direct to ABBOT waypoint,although it is actually based on a VOR (BKY) radial and distance it would be ridiculous to try and navigate to this point using VOR radials/cross cuts etc.
try and search for "GPS approved for BRNAV" in google
hope this helps.