The only problems we had with booking.com is that they give you no protection whatsoever. One case, the hotel clearly gamed the reviews and posted false info. It was so bad that we had to leave. But we were still charged the full amount, and booking.com just stood aside.
Just recently, my wife booked a hotel in Tel-Aviv. The hotel charged her card twice (booking.com seemed to have passed the card info to the hotel). We cancelled, and still waiting for the refund/release of the funds. Booking.com does nothing to help. We have to bounce between the unhelpful hotel and the slow-as-hell bank/credit card company.
OT: but are there any banks or credit card companies in Germany that actually help you when you're in this situation or need a chargeback? it seems like the low card fees in EU means much worse customer service compared to the US, or is it just my wishful thinking?