Actually you can setup Google Talk to be a universal client, and talk to MSN, AIM, ICQ and Yahoo all at once from the same interface. I wrote down the steps to do just that at
http://francks.blogspot.com/2006/02/...eb-client.html. Once it's done your gtalk client on the Blackberry will be able to replace all those universal IM clients and connect to all possible buddies....
I could not test because I live in the UK :( and even though I was able to download the client by pointing my proxy to a box in the US, I get an error that some service books are unavailable still. Any help on that would be appreciated ;)