I struggled to install it, to use the extension directory (which could be much better organized) and to customize it. I wanted to use it for a book store, and only found one theme that could accommodate books. However it was a commercial theme and didn't look so good, so I ended up just using the default theme.
Despite all its faults, other extensions pale in comparison. So I used it for my site anyway.
I contacted support when I got stuck (as a result of my own inexperience - it was my first Joomla website - not the fault of the extension) and the support was incredible. Personal, informative and very helpful. Five star rating for that.
Loses one star because it failed a bit under the load of many documents, but I was testing the boundaries and it didn't affect the usability of the site.