One part I was dreading was having to redo my entire document library from scratch.
Fortunately, the DocMan team have an "exporter" function for DocMan 1.5 (Joomla 1.5.x) and greater, and then an "import" function for the latest version.
Unfortunately, it didn't work, but within about two days of reporting the issue on their forum, the development team had diagnosed the problem, installed a patched version on my site and the export/import then worked flawlessly; all that remained was to copy across all the document files themselves. Many, many hours of work saved. This patch will apparently be in the next release, so hopefully everyone should have a smooth experience. All my categories and documents and descriptions seem to have come across flawlessly.
In terms of the component itself, it does pretty much exactly what you'd expect it to; it integrates well within Joomla and manages my documents very nicely.
Yes, it costs money, but you tend to get what you pay for...
Initially, I couldn't get it to work in Joomfish - but then I re-read the post and worked out that I needed to get the XML file available from the download page and included that, and now, it's working perfectly.
Thanks for a great extension!