Well that's the thing, none of what anyone says here is a straight up fact. For the most part, it is impressions that people collect while listening to different products
I personally prefer reviews that are almost entirely based on emotion instead of an objective evaluation of a product - for example I love aminus (or animus I'm not sure) and how dead honest he is about hating just about everything that's put out. Maybe he exaggerates here and there, maybe he doesn't - either way, he's conveying his emotion and emotion alone, and if my preferences were aligned with his, I'd say what he writes would be significantly more useful than a lot of other stuff
It's more the responsibility of the reader (IMHO) to filter through the reviews and find out what he is interested in. Just now, for the sake of the experiment I scrolled through 6 Penta reviews, and not one mentioned just how thin the midrange is. On head-fi things were a bit more straightforward, and people actually pointed out what the midrange is like. Oddly though, they gave it high ratings but then went on to describe how it has mediocre soundstage width and depth, no treble extension and a generally thin and characterless midrange. The only review that I felt was able to accurately convey just what the Penta is like, is that of aminus.
I've based some purchases off popular review sites, and compared my impressions with that of the reviewers, but what I was hearing was COMPLETELY different from what they were describing
I do understand the point that it only really makes sense to review stuff you enjoy, and I do the same - I feel it's often the case that it's not really worth the investment to describe how much you dislike something, but there's also a lot of fluff pieces out there - again, IMHO