I am also looking at some sort of VOIP implementation in my organization. I am the IT guy for the entire Hawaii region for my company. I have been reading about the benefits of VOIP so now I am trying to built an project to put it to use. I have been in touch with PingTel and I am about to place an order with them for a SIPexchange server and some hard and soft phones.
Eventually I would like to move all 500 users on out LAN to VOIP phones.