Thanks to Born2kill and Winston for the info.
An internal development build of Mirabilis' ICQ 2002a has been leaked to the web! Build #3706 features major performance improvements and a somewhat revamped interface, which does now also support the Visual Styles found in Microsoft's new operating system Windows XP.
News source: ieXbeta.com
Download: ICQ 2002a Build #3706 (ieXbeta.com - 3.85mb)