For what it's worth, the features that I use are:
- Importing books. I also add paper books as empty records, and add audio books (if the audio book is a single MP3, I add the MP3. If not, I add the files to a gzipped tarball and add that)
- Converting between formats
- Clean up/fix metadata (usually consists of adding my own tags, and adding a description)
- Some books go into a hierarchical set of custom columns. For a while, I had those in a separate library, but I've now decided that this works better for me
I've used the Get Books function a few times.
The only plugins I use have come from Apprentice Alf.
I like the the news download function, but I found that I never actually read the news that I downloaded, so I don't use it any more.
I've also used the donate button