The ULLtraDIMM SSD will come in 200 GB and 400 GB versions. Its direct link to the CPU allows it to boast a write latency of less than five microseconds, 150,000 input/output operations per second and one GB per second of sustained read/write performance per DIMM slot.
These drives will be gnarly-fast and, should you be lucky enough to get your hands on a pair, will be an excellent thing to stick in those spare DIMM slots. They are currently billed as "enterprise-class" so don't expect to see them in your economy-class desktop anytime soon.
There's no definitive word on a release date or pricing yet, but stay tuned.