Thanks for the reply - the problem turned out to be an incorrect setting of some timeout values. Over 99% of the packets are now received with some decent power savings.
Now, the one really weird problem I'm seeing while using listen mode and a less sensitive RSSI threshold (register 0x29), is a packet will fail to transmit, no interrupt will be generated but the status register say something happened. Nothing appears over the air. If the code waits a 250 ms and retries the packet, everything works great. This only happens if the chip initiates a "cold" transmit (i.e. not in response to a received packet) -- maybe 20% of the time. If the chip is acking a packet, the failure-to-transmit is never seen.
A RSSI threshold of -110dbm to -120dbm everything works great, -100dbm or greater (going towards 0) will increase the frequency of the transmission failure.
Another data point, this failure is never seen when using a normal receive mode, only listen. The sequence to transmit is, listen mode is aborted, placed into standby mode, the fifo loaded up, and then placed into transmit mode.
My understanding the RSSI threshold is only for receiving, but some how this is triggering a bug with transmission?
-- Michael