My home screen is now much less cluttered with only one IM app icon. While chats are not yet integrated into the 'Messages' list the app is fully integrated with the profile manager and notification zone.
The bubble style chat looks great and the app shows the current time and network coverage at the very top, not something I thought an IM app really needs, but its actually very handy if you are trying to chat in an area with patchy coverage...
Check it out for free from http://www.trillian.im/get/blackberry/