On check-in they asked us to fill in a paper form with our card info - including the CVV2 code. I am almost sure the bank would advise against giving away your CVV2 code on a piece of paper - pretty insecure. They say they need this as a warranty. I have refused so than they asked to pay a cash warranty. I told them that I am not paying anything because no such thing was ever mentioned on the booking.com terms. They said I am correct and gave up the idea.
Once I got into my 5* hotel room, I found that the carpet was full of dirt. 10 minutes later, a made knocked at the door with a vacuum cleaner telling me "problem, problem". So they knew about the dirty carpet, just forgot to clean it before giving away the room.
During the stay I have found that the WIFI was accessible only in the lobby of the hotel, if you were stepping out just a few meters to the hotel's restaurant or pool area (still public areas) there was no free WIFI available, only paid. Frustrating.
And finally, on the checkout, I found out that I should have done a stock take on the minibar on check-in. Haven't took anything from it and I was told that I had some juice and I have to pay for it. I haven't argued, I couldn't prove them wrong, so I just paid it. Only a few euro, but frustrating.
What was good about it: Facilities - indoor pool and gym, the restaurant, the food, the general look and feel of the place, the staff - very professional and friendly, most of them do understand English.