WinPack certainly offers an impressive list of features; however, there are a number of missing features that would make it an even better client. Providing a front-end for virus scanning of archives (for the 16-bit version), a more extensive online help documentation system, integration with the Windows Explorer, right mouse button functionality, and support for LZH compression are a few of the features currently absent in WinPack.
And when you combine these missing features with the fact that WinPack hasn't been updated in over two years, it's easy to see that WinPack has its work cut out for itself if it expects to remain a contender in the always evolving compression scene. (And considering that the main WinPack Website no longer appears to be available, it appears WinPack might have bowed out already.)