This is interesting because there are only 2 connections instead of 3 (lately, since getting into twi, I've been wanting 4 connectors.) This is much simpler than using 3 connectors from the circuit design standpoint, however it seems it would be a problem when designing digital devices, such as arduino or number bits.
I hope William Ribeiro does join us - I'd love to hear how he mixes his power and signals into a single line. I've read of, but never used something called a one wire interface.
ps, I want to see more of his robot work as well!