... The key difference might be that Vista uses SMB2.0 protocol (which has improved performance), compared to XP (assuming that you were testing on XP).
Agree, such might improve situation yes. XP was used for bluray sharing, but have also tried some HD content from NAS drives and linux cifs&uPNP shares. Some solution could benefit from jumbo frames etc, but I did not bother to study bottlenecks as upgrading to 1Gb lan meant less than 50 Euros for a new switch.