Sectorized antennas can increase wireless network capacity through greater spatial reuse. Despite their increasing popularity, their real-world performance characteristics in dense wireless mesh networks are not well understood. This paper conducts a systematic experimental study on a mesh network testbed using commodity 802.11 hardware and multisector antennas. Our study results in the following main observations. (i) Sector selection should be based on explicit measurement in all sectors, though the measurement overhead can be significantly reduced by exploiting spatio-temporal characteristics of the best sector. (ii) Multi-sector activation typically reduces the signal strength of a link compared to single sector activations due to antenna design constraints. (iii) Spatial reuse is constrained by characteristics of antenna radiation pattern in different sectors (iv) Physical layer capture reduces the effect of directional hidden terminal problem. Finally, we discuss the implication...