The Samsung SSD 840 Pro is by far the fastest SSD currently around- faster than the OCZ Vertex 4, faster than the Corsair Neutron GTX and faster than the Plextor M5 Pro. Samsung also has a proven track record in terms of reliability and quality, as the Samsung 830 series had very few known issues. History is of course not a guarantee for future success, but there is no reason to think that the new 840 Pro series will be any less dependable.
The recommended retail price of the Samsung SSD 840 Pro 256 GB will be around £222, which translates to £0.87 per GB. That's not cheap, but still comparable to the very fast Plextor M5 Pro. For normal desktop use the more affordable Samsung 830 is probaby a good-enough option. The reason is that the PCMark 7 benchmark proves that for normal consumer use, modern SATA 600 SSDs differ very little in terms of performance. For professional use, on the other hand, raw performance is more important than the price. Right now, there is no faster SSD available than this 840 Pro.
Samsung SSD 840 Pro 256GB