An opportunistic feedback protocol with maximum throughput (MT) scheduling has been proposed in the literature to achieve multiuser diversity for the downlink transmission of a wireless system, and its system capacity has been analyzed with the assumption that the received signal-to-noise ratios (SNRs) for the users are independent and identically distributed. In this paper, fairness and capacity performances of the opportunistic feedback protocol are analyzed for SNRs with independent but not necessarily identical distributions. In addition to MT scheduling, we also analyze the fairness and capacity performances for proportional fair (PF) scheduling. Compared with MT scheduling, numerical results demonstrate that the PF scheduling achieves strict fairness at the cost of about 10% system capacity loss over Rayleigh fading channels. Moreover, the feedback threshold and random access probability of the opportunistic feedback protocol are jointly optimized using a constrained gradient descent method to maximize system capacity.