I've owned a classic Big Berkey for about 10 years. The filters, while expensive, are the best of their class (gravity fed). You can see, taste, and smell the difference.
I don't know how impartial waterfilterlabs.com is, nor how rigid their testing methodology is, but the top of the line Berkey filters (the black plus the fluoride filters underneath) rank the highest on nearly every category. The systems were designed to filter questionable water in shitty, war-torn, 3rd-world environments, so they knock out pathogens, volatiles, and heavy metals.
Just because quacks may recommend a product doesn't necessarily mean it's snake oil.