Extreme densification of base stations is imminent in the next generation of cellular networks to meet the exponentially increasing demand for mobile data traffic. In such ultra-dense networks (UDNs), the remarkably high inter-cell interference can reduce or even negate the densification gain. On the other hand, directional communications can significantly bring down the interference levels in UDNs. Hence, it is of importance to evaluate the network performance of UDNs with directional communications. Through Monte Carlo simulations, this paper analyzes the characteristics of coverage probability, area spectral efficiency (ASE), and per-user throughput with respect to extreme network densification. Our simulation results show that directional communications can deliver significantly higher network performance with tens of times higher ASE when compared to non-directional communications in UDNs.