So, along with the release of The Unarchiver 3.0 comes another new things: The Archive Browser. This is the often-requested version that lets you browse archives and preview their contents before extracting. However, since this is not a program that I personally need, this one will actually cost a few dollars. Buy it if this is what you really need, or buy it if you want to support the development of The Unarchiver!
http://itunes.apple.com/app/the-archive-browser/id510232205?mt=12&ls=1
http://archivebrowser.c3.cx/
For now, bug reports and feature requests can go on the The Unarchiver bug tracker:
http://code.google.com/p/theunarchiver/issues/list
It is much better to post them there than in this thread, because I tend to forget things that are not on the bug tracker.
This is what I get on Mountain Lion, regardless what file I'm trying.
Any ideas?