Pros: I bought two of these online for only $99 each. For a total cost of only $200 I was able to get 146GB of RAID-0, 15K RPM speed that rivals the fastest SSD drives on the market, with far better reliability and longevity and none of the SSD drawbacks.
Cons: $200 is still a disproportionate amount for "only" 146GB of storage, but it's not an issue in my case. They're 3.5 inch drives, so they will take up two full-size HDD slots. 15,000 RPM demands both adequate power and ventilation for cooling.