Have you found this tool to be actually useful?
I like how you qualify that with "actually
As that is exactly the point - wherever you encounter something which throws numerous and verifiable
false-positives, one kind of loses faith in the product as a whole. Personally, I consider it wholly unreliable for MP3's - as I retained the original FLAC's used to generate them (using MB's latest lame aiming for 320 CBR), FTF would quite happily accept/verify the FLAC's as fine, but the MP3's were (according to FTF) sometimes wildly divergent. I could accept the odd misinterpreted 256 rate here and there, but it rather laughably decided that almost an entire collection of Erik Satie music was magically only 64 bits. Admittedly, Satie is quiet solo-piano, so the spectrum may not challenge some fancy Pink Floyd remaster (or whatever), but if the FLAC was fine two minutes ago, how did the spectrum shelf drop so precipitously? Obviously, it didn't, so false-positive. Just one example.
Out of an entire collection of around 30,000 tracks it rejected just under 2,000 of them (some legitimately, as I knew they never had reliable sources to begin with, and had been mistakenly upscaled), but after verifying the sources of the rest (and re-ripping, just in case I was at fault originally), I concluded that only around 100 were legitimately dodgy.
So... "actually useful"? Hard to say... it spurned me to spend an afternoon re-confirming my collection, but that's about it - I keep it installed just to see what it thinks of any new downloads I get, but "grain of salt" comes to mind. That being said, as popular sites like Bandcamp don't actually claim any responsibility for the originating quality of their downloads (the artists themselves hold that obligation with the sources they provide), that grain of salt begins to transcend the quaintness of being a mere pithy-saying to becoming a proper phrase-to-live-by.
If nothing else, Fakin' the Funk is a really good tool to needlessly scare the bejesus out of unsuspecting beginners who put too much faith in superficial numbers... and automation.
Just my opinion, anyway, for what it may be worth.