Based on the information available, I don't see that on balance Empower is better than iChat AV for voice chat. Call me a moron.

iChat, I know, works well on 28.8kbps connection, don't know about Empower, but it lists 56k as min. Empower might be overspeccing, or might be using an inferior codec. I don't feel like finding out, yet.
iChat is free with Panther.
iChat requires no fiddling with Airport.
iChat can connect to Windows users in the latest version.

Empower appears more configurable, so if everyone I know had a blazing connection, I could talk to them in CD quality. A moot point for me, however.

So if all my friends had high-speed, none of them owned PCs, none of them owned Panther, and I didn't have Airport, I might make the effort to convert people to this. As it is, I see no compelling advantage in doing so. Can someone tell me otherwise?