Version 2.2, which purportedly "works" on Leopard does NOT, in fact, work on OS X 10.5.1! Raising the issue has yielded nothing but silence on the developers Blog (http://tinycrumb.com/blog/ichat-matte-2). Great idea but just not happening..
Ya... it looks clean but it seems to be limited to only the main colors in the prefs. If you try to use any of the "other" colors the bubbles come back.
So with that being said... I was thinking of uninstalling it but there isn't a uninstaller.