I find that the RTC sync function seems to set the mbed clock several hundred ms late (relative to my net-sync'd PC clock). I'm using Andy's included example1.cpp. I this as simple as the delay to display? My ultimate use needs better precision (10ms). Any ideas/ thoughts?

It depends on your system, do you need 10ms absolute accuracy, or only relative between two (or more) locations. And most likely the code just sets the seconds correct, not below seconds, so you might need to change something there.

Hey Erik. I'm trying to sync up to a global HF radio beacon network which is itself sync'd to nist (I think). I believe you're right in that I need to correct at a sub-second level. Any idea how to do that feat?? Thanks..

I don't know exactly what GPS sends, and what the library does (link to it might help). There should probably be an option on the chip to clear the prescaler, so that moment is considered the start of the new second. However that only helps you if you also get that data from the GPS device/library.