I'd say, like most online stuff, I put some weight into them in the absence of other information, but would not really rely on them for a high impact decision. When we're talking about a restaurant or something, there's only so much effort you can put in to confirming past performance before you're better off just trying it. Which is guess is what some places are banking on, e.g. those that rely on reviews to drive customers in, as opposed to catering to community or regulars