Alas I don't know of any, but I'd be interested to know if there are any good ones.
When I'm hunting for snowboard info there are too many "vague and useless" reviews. Sometimes I think we are spoiled by sites like TR and Anand since outside the tech field, impartial yet informative reviews are pretty hard come by. Possibly the Auto industry is the only thing that comes close.
As a rule, I look at customer reviews on the bigger sites and just look at the criticisms. Looking at the positive reviews, most of them are "OMG THESE ARE AMAZING" twitbook/facetube-style comments, which you just have to ignore because people typically buy a better and more expensive model when they come to replace old gear, so uh.... of course they're going to feel better than your old ones, you morons....
Anyway, you find the good ones by eliminating many of the bad ones. I could recommend some snowboards based on the experience of me and my usual boarding buddies over the last dozen trips, but my skiing knowledge is pretty crap.
Some people ask me why I have always enclosed my signature in spoiler tags; There is a good reason for that, but I can't elaborate without giving away the plot twist.