So my wife and I booked an apartment for 3 nights to celebrate our wedding anniversary here in Hungary, Budapest.
Our experience with using booking.com was a nightmare. The guy from Emerald gave us a different apartment which was 3 times smaller than the one we were supposed to have. He was very rude and even told us we can cancel the booking if we want. (the cancellation costs is equal to the price for renting the apartment which for him was an excellent deal)
We decided to stay in the smelly, ugly and very dark apartment rather than staying on the street...
I definitely do not recommend booking.com I think they should be responsible for the service of those businesses that are using their website.