ArduPilotMega 1.02 is now available in the download section. This version updates the GPS libraries to support the new v1.6 firmware that adds some useful data fields and otherwise makes HappyKillmore's GCS, well, happier.
New MediaTek modules shipping from the DIY Drones store have the 1.6 firmware. If you've got one of those or have updated your module to 1.6, you can use it with APM by selecting "GPS_PROTOCOL_MTK16" as your GPS protocol in APM_Config.h.
If you want to update your GPS module to 1.6, here's what you need: