I don't trust reviews in any capacity except one - if there is a critical mass of immense praise from actual players for a non-AAA game, it's got pretty good odds of actually being good. From game review businesses? No thanks, not a chance.

I play demos INCREDIBLY rarely, although the Talos Principle "demo" sold me on it, that's one of the rare examples I can think of. On Steam you can always just return games if you play them for 2 hours or less at will, so demos are not very useful.