Confirmed. GPS works at boot-up in rc1, does not work rc3. I have also tried reverting to the previous Linux kernel (currently on 4.4, reverted to 4.1) and that makes no difference. So I have to conclude that something has changed with rc3.
Also, if I log in, kill arducopter, and restart it, GPS seems to work. So it is something happening when I autostart it at boot time. This is why it always works for me at home. I kill arducopter and restart it with the -A udp:(ip address) flag so I can communicate with it via Mission Planner, and miraculously, GPS is working.
Any troubleshooting tips on how to get GPS working again for rc3 would be appreciated! Are there any parameters I can set to force it to continue looking for GPS?