MLC (multiple level cell) NAND technology allows for higher density of data storage capacity. This could greatly lower costs for data centers by up to 4 times. There are still some performance, reliability, and endurance issues to work out but the technology looks to make solid state drives a household product.
SLC (single level cell) NAND memory can store 1 bit per cell. This allows for higher read/write speeds and up to 100,000 write cycles. MLC NAND memory is capable of 2,000 to 10,000 write cycles but can store multiple bits per cell meaning more storage capacity. As well in order for MLC to function properly complicated firmware is required to handle data allocation and organization. (link)
The main problem with SSDs has been write performance. The fixed block sizes forces inefficient handling of data storage. Data is spread out evenly across the flash memory but slows access time and increases wear and tear. Adding RAM buffers can speed up read/write times.