The pendulum swings toward SIP
From their site: “Using pulver.Communicator/XP, subscribers to the FWD Communications Network can enjoy Instant Messaging with their SIP contacts, as well as with their buddies on the four most popular IM networks as well (AOL, Yahoo!, ICQ, and MSN). And not only that, but pulver. Communicator supports multi-party chat across the different IM networks”
I couldn’t get this to work very well but it is only in beta. This new SIP client has some good new IM functionality which may help promote VoIP among the current IM community. Messaging functionality was a distinct feature of Skype but now they are only really ahead on free voice conferencing. See here for more on VoIP.