I would describe the OCZ Agility 3 as the typical mid-range SATA 6 Gbps SSD. It offers a decent 10% performance upgrade over "old" Sandforce based drives which support only the 3 Gbps interface. Compared to the more expensive Vertex 3 Series, we see a performance reduction of 10% again. Since the Vertex 3 costs over 10% more, the Agility 3 offers slightly better price/performance, too. When looking outside the Sandforce universe, we see Intel's flagship 510 Series beating the Agility 3 by 14%, but the Intel drive is much more expensive. Crucial's C300 / M4 is the current price/performance king in the SSD segment.
Overall, the Agility 3 is a good investment, especially if you have a motherboard that supports SATA 6 Gbps.