I made a mostly negative review about a NYC hostel a few months ago and that's still up there.

Can't say I've had any real problems with the reviews there. I agree with some of them based on places I've stayed but a lot are dependent on what room you get as things like excessive street noise, poor furnishings etc sometimes only apply to a few rooms.

Been looking at hotels for Washington DC and they all seem to have problems regardless of whether they're $400 a night 5* slap bang next to the White House, or $200 3* 20 minutes walk away. I tend to read reviews based on chains or brands that I've heard of or some place mentioned by someone else - that's how I heard about my last NYC hotel (wouldn't have considered it due to it being slightly further out than the usual touristy areas but some people on another forum were singing its praises and I took a look, booked on the strength of reviews / recommendations and price and loved it).

I personally like reviews from a few sites before I make my mind up. Some of the booking sites just use Trip Advisor or +ve reviews only so I don't pay too much attention to them.
Somewhere like these forums has people travelling all over the world and I've learnt quite a few hotels in places like Hong Kong, San Francisco etc that whilst maybe classed as the best and get rave reviews, aren't as good as another in say the same chain.