Anybody got experience with Voda and Optus 3G wireless?

I know they use the same network infrastructure so 3G coverage shoudl be same.

I'm interested in the roaming from 3g-WiFi-GSM. Optus advertise that their product has seamless roaming (user won;t notice as you move from one net to the next). Does Voda have same? Does Voda even link with a WFi hotspot provider?