While it's pretty hard to imagine why they'd bother, Cerulean Studios is porting Trillian, their wildly successful Windows multi-IM client, to OS X. How will Trillian (a commercial product) compete against Adium (a free product), particularly considering that Adium is a number of years ahead of Trillian on the Mac, and is by all accounts a very strong multi-IM implementation? As someone who used Trillian for a number of years in Windows, I can say that Adium has completely met my instant-messaging needs on my Mac. I'm what you might call a heavy IM user, with 6 accounts that I use regularly.
Now, to be fair, Cerulean Studios states that this is in fact not a port at all, but a ground-up reimplementation of Trillian. The teaser screenshot on their announcement page is certainly intriguing. From the announcement:
Though this first alpha build of the OS X version of Trillian is still very preliminary and minimal - the functionality pulled through is about the same as the Flash-based web version - the code for every single feature on the Windows version is there in the underlying mediums. As the UI is expanded, those features will become available. The OS X version will be playing catch-up to the Windows one for a while yet, however.
Currently it appears that test versions are only being offered to testers of the current Windows-based Trillian Astra. Click through to the announcement page if you'd like to sign up to test Trillian on your Mac.