From France, we are on booking.com as well. They have taken over the market down here. Not just for hotels. They are now on a big push to get holiday rentals, B&Bs, campsites, ... Any kind of accommodation will do. We see many small B&Bs with 1 or 2 rooms joining them.
People are less and less googling for "Hotel Paris" and more and more for "Booking". We get a third of our bookings from them and they help us fill-up off-season weeks. We close availability in summer and spring's week-ends.
Expedia/Venere/Hotel.com sends us peanuts in comparison. Their extranet and websites are very poor compared with booking.
Commission is also 15%. It is said that about 30% of their visitors will book directly at the hotel. We exclude cost of breakfast on booking so that we pay less commission. A portion of those guests will come back or recommend us. We are strict on cancelation terms and withdraw from guest's CC if allowed. The guests they bring us are guests that we could not get otherwise : most of those guests went directly to booking.com without going through Google. All in all, both sides are winners.
I understand that share holders' concern is that booking.com's profit growth continues. To do that, they need more stock (yes, that's us). Thus their push on B&Bs, campsites, ... It is obvious that they will look closely at the US market. Get ready.