I don't see it taking away Adium's lead. I was glued to Trillian when I used Windows as my primary OS. Unfortunately, Cerulean studios chooses to keep their software's source closed, and their release cycles are terribly, terribly drawn-out. The last major update for Trillian was nearly three years ago. There are huge gaps in their development cycles, and their betas are often closed.
Adium, on the other hand, has frequent updates and open betas. The same is true of Pidgin, which I feel is currently superior to Trillian on the Windows side. This is a clear case of open source trumping closed source. Trillian, I am sad to say (as I used to love it), is old news.