It may have some bugs but there is stuffit too, so there's no problem.
The ADVANTAGE is : pax!
It's able to decompres .pax files, so if you have an installer and you don't want to install the hole thing, you can extract only the parts you need without having to buy the installerextractor whose name I forgot.
Control-click the installer and select "show packagecontent" or something similar (just below the colorlabels), then look in Contents for Archive.pax.gz and drag it to OpenUp. You'll find every item that would be installed.