I had been trying FoxTrot Professional Search for several months before eventually deciding to buy the professional version. My initial motivation was to find a tool that could search inside Papers3 library, but I have discovered that the appeal of FoxTrot is much stronger.
There is no one-size-fits all search engine. Files that are used or have used recently can easily be found through a simple Spotlight search or even navigating to their specific folder (e.g. through LaunchBar where I index my most frequent folders). The speed of getting to the right file really matters if you need it several times a month. But many reference files used in academic work are not like this. You definitely don’t remember their name, but you may have tagged them for a year ago and/or you may remember a particular term or phrase in the text. To find such ‘needles’ in your ‘haystack’ you really need a professional-grade search tool and so far FoxTrot is my favorite choice.
FoxTrot’s UI is not exciting or super-sleek but it’s very clear and functional. The app gives you a feeling a good search engine should provide: ‘Aha, good I found this one! I’ve completely forgotten about it!’ (instead of ‘Oh. What does this one have to do with what I am looking for?‘). And, yes, it does seamlessly search within Papers3 library as if it was just another ordinary location (the recent Papers3 version already allows Spotlight search – and yet I often prefer going through FoxTrot to find out what I need).