The Agility 4 from OCZ has its low price as the main selling point. About £160 for a 256 GB SSD is very competitive, but OCZ isn't the only manufacturer of solid state drives that wants a piece of the pie. The Crucial m4 and Samsung 830 cost about the same. We put the three affordable SSDs side-by-side so you can see how they compare here.
Overall the Samsung 830 comes out on top, it has the best performance especially when you look at the most important benchmark (PCMark 7). So if you are looking for an affordable 256 GB SSD, we would right now recommend the Samsung 830 and not the Agility 4. However, the SSD landscape is evolving rapidly, so keep an eye on prices.