I am using DocMan since Joomla 1.5 and must say: I won't miss it! Whenever it comes to a large amount of documents and files, Docman is my first choice! The easy setup of Categories, documents and permissions offers an easy workflow, even on professional and commercial websites.
The DocMan 2.0 UI is even more user friendly. I enjoy the batch assignment of many files into one category, it is so much easier than in the old DocMan!
The support of the developers is also worth mentioning. I use DocMan 2.0, which is in state of RC right now (Dec 2013). Though it is really much better than DocMan 1.x, some features are still missing. The staff really took care of my issues and fixed them within 24 hours. This is what I call a support!!
I also managed to upgrade my DocMan content from Joomla 1.5 to Joomla 3.x with their great migration tools.
If you handle with a lot of documents, buying a subscription will save you time and nerves ;).