It is a free utility and that is much appreciated. There are some bugs that are annoying but it is useful overall.
In particular, when opening a zip file, Zipster closes the folder that contains the zip file. Very annoying and disorienting. This forces you to have to open the folder that contains the folder that contains the zip file before opening the zip file... to allow you to maintain your context in the finder after hipster changes it.
A new one that I found today is where a zip file contains folders and you create a new one, then try and move an old one into the new. A dialog opens telling you that whatever you are moving is already in the empty target folder.
Overall, this idea is good but the implementation suffers a bit. I keep it in spite of the bugs and owning BetterZip because "less is more" but the first bug is why I only use it on occasion.