My problem with the 'new' IMs is the one that's endemic to any new service of this nature.My friends are all on YIM, AIM or ICQ - and I don't particularly feel like being a cheerleader for a FOURTH service now.
Hotmail tried for a while to do an "all in one" messenger that would be able to recieve both HIM and AIM messages. AOL successfully legally blocked them. I would imagine that any attempt to create a third party program that would allow you to operate and recieve messages from several other services would probably run into the same difficulty eventually.
Good luck with it though - if you like it, and can get enough people on it to enable you to remove the other IMs, more power to you.
M