Unfortunately, the onboard S/PDIF lost a lot of its coolness with the death of Soundstorm.
On a nForce 2 w/ Soundstorm, the onboard sound can encode all of you audio in real time to Dolby Digital 5.1 and output to a home theater PC. This made the NF2 a great platform for HTPC builders.
With Soundstorm gone, though, the onboard S/PDIFs only acts as a pass through for audio sources that are already encoded in DTS or DD.