I also haven't yet met a Culture novel I didn't like; but I'm astonished by your ranking of them, which is nearly the opposite of my own. (I also preferred Consider Phlebas over Look to Windward). The books I've read but you haven't yet gotten to (Excession, Inversions, Surface Detail) are my favorites (in increasing order of preference); I would be very curious to know if they turn out to be your least favorites, in decreasing order...