[Koha] Open Source ILS Add-ons

I am preparing for a one hour webinar on Open Source ILS Add-on products. By "ILS Add-on," I mean products that extend the functionality of the ILS and wish seem to fall into three main categories: discovery interface, and metasearch. If you are using, have used or have knowledge of any of the following products, I'd be much obliged if you'd tell me a bit about your experience. Like it? Love it? Using it? Know it is dead? Know something better? You know it works with Koha/Evergreen/anything else? Thanks in advance! Discovery Interface products: SOPAC2 Blacklight Kochief Scriblio VuFind XC Metasearch: LibraryFind Pazpar2 dbWiz ILL: Relais (not quote OSS yet?) PLEIAS