If you aren't using this, you're doing your users a huge disservice IMO. This helps my users quickly find similar content that they want to add upon. It improves posting, especially on busier communities.
Loved this on XF 1.5 and love it now on XF2. It was one of those addon's I knew I had to keep around after the upgrade, because people would definitely complain about it being gone. In fact, it WAS missing for the first day after upgrading, and people already WERE asking about it. Essential, as far as I'm concerned.
Great Addon! I paid for this one, but get a lot more. All addons from AndyB are available within this payment. Andy also gives a very good costumer service, he's been bussy for a few days with my website, and I don't even know this nice guy. This 25,- USD is the best investment I did for XF2.