I currently have 1500 desktop machines using AD 2008 & OD 10.6.5 for computer management with about 300 Imac’s running 10.6.5 and 150 running 10.5.8 our network is Gigabit Ethernet from top to bottom running on 5510,5520,8600 nortel equipment we also run voip over same network and we have had no problems mounting smb shares from macs nor have we had any problems with speed.