Why negative reviews on USB with newer USB DACs?

I switched over from a CD transport as primary music source to a MAC Mini music server about 1 1/2 years ago using the USB output to my DAC via a HAGUsb converter. I found the results far superior than any cd transport I used with S/PDIF coax connections to the same DAC. Over the past six months I keep reading professional reviews of USB DACs like the Stereophile review of the Bel Canto DAC 3 and the Six Moons review of the Cullen Modified PS Digital Link III where the reviewer was unimpressed with the USB input vs. the S/PDIF input of the same DAC. I find this a little bewildering with all the reported successes on this and other forums with Lossless based hard drive music servers being vastly superior to tradional CD drives via the USB output. The professional reviews lack specifics so it's hard to know if the computers used were optimal in setup, e.g., loss-less files, cables, etc.. I'd be interested in hearing from other forum members who are dissappointed that professional reviews are sending a message that USB is not the way to go when if fact it is!

A few other details on my systems: HagUSB is AES/EBU version. Connected to the XLR input of my PT 1A/PT 3A/ Monolithic P3 digital front end. The USB cable is a Belkin Pure AV. The power cord for the MAC Mini is BPT L10 with Oyaide 079 ends connected to Oyaide AC outlet. BTW, the PC upgrade from stock PC brought a remarkable improvement to the sound from MAC Mini. And all files are Apple-Lossless.