'SSD' is not something new.The 'SSD' has been around for years. Density as it has increased has provided smaller foot print drives. DRAM based 'SSD' are still used but with the NAND based 'SSD' you have the reliable backup without battery backup that is required for a DRAM based drive. DRAM based drives won't have wear problem as with a standard hdd. Access is much better with a DRAM based unit and has been used without difficulty. DRAM based are larger than the new 'SSD' based on current NAND technology but with the potential degradation. That problem is moot if you look at the numbers.
The hdd with increased platter speeds is one of the ways to have better throughput. Add to this the increased buffer space and the drives are still usable. With density increasing for memory we will see bigger and better DRAM based 'SSD' technology but not for the general desktop user at affordable prices.