The 802.11ac is a significant landmark in wireless communications, as it pushes towards new rate limits of more than one Gigabit per second, utilizing downlink multiuser multiple-input multiple-output (MIMO) beamforming to transmit data to various locations simultaneously. However, successful beamforming relies on intelligent user selection which requires extensive overhead of channel calibration between the AP and each of the candidate users, which hinders the utilization of multiuser MIMO. Thus, the subtle relation between the achievable rate of a scheduling algorithm and the overhead it requires is significant for the 802.11ac performance analysis. The significance of this paper is in the rigorous analysis of distributed scheduling algorithms for the 802.11ac, which holds even when the number of users is moderate. In particular, we accommodate common scheduling methods for the 802.11ac protocol and analyze their expected achievable rate. In terms of throughput, both analysis and extensive simulations depict the superiority of simple threshold-based methods.