At the moment A-DATA's S599 128 GB is the cheapest 128 GB Sandforce SSD available on the market. It uses 8 GB of overprovisioning, whereas many other drives use 16 GB. Our testing shows that this does not have any negative effect on performance at all, actually the A-DATA S599 is the fastest Sandforce based SSD we had in our labs so far.
The only real point of criticism I would have is that A-DATA advertises the drive as "128 GB", whereas it has only 120 GB usable capacity. According to A-DATA, the "total advertised capacity is the actual amount of NAND flash memory used, it may not be directly accessible but is given back in the form of endurance, write amplification, and performance".
The SandForce SF-1222 packs the much talked-about TRIM feature supported by the latest version of Windows and Linux. The garbage-collecting capabilities of TRIM could become extremely important in the long run, as the drive begins to age. Unlike with magnetic storage devices such as hard drives, where new data can simply be overwritten on top of existing data, for NAND-flash based devices, the portion of the flash chip must be physically erased first, consuming some write cycles. TRIM makes sure that the drive knows immediately when blocks are freed after a file delete which give it a chance to wipe all portions of the flash chips "clean" when the drive is idling, so the cleaned areas are ready to receive new data, faster. Without TRIM, the drive would have to waste those write cycles whenever the OS seeks to write data, which happens to be occupied by deleted data, and that lowers write performance.
Overall A-DATA's drive is the fastest and cheapest 120-128 GB SSD right now, with leading performance scores and great Performance per Dollar and Performance per GB.