It's weird to see all those negative anecdotes about Booking.com. As a counter anecdote, I've used them several times and they always seem to have much cheaper prices then the competition. I was also able to cancel my booking once without issue after talking to customer support. PS: Not in any way affiliated with them other than being a satisfied customer.
It's not weird at all, most forum threads involving huge companies attract largely negative comments (Google, Amazon, even Apple). By and large I'm happy with the services of these companies, but if you go by HN I can get my gmail shutdown with no reason or recourse and half the stuff I bought from Amazon is probably fake.
It's not just huge companies, it makes sense that reviews for anything usually skew negative. Because if someone orders a product/service that worked out great, not many people take the time to write a "thank you letter." But if something was amiss, the user will have no problem venting their (warranted) frustration. I would be livid if Gmail locked me out of my account for no reason, or I received a fake product from an Amazon seller, and would certainly let people know.
However, on the same note, I hate when I see someone blasting/suing Walmart or similar for what one cashier did to them. No amount of corporate training can prepare someone for a bad day.
I've used them - and will in the future - because my wife likes being able to take a bath, not a shower (long hair is hard to keep dry in a shower, but in a bath she just puts it in a ponytail), and curiously enough booking.com is the only site I've ever found that let you use that as a search criterion.