Although our synthetic benchmarks were a bit inconclusive, this device does exactly what it is designed to do - breathe new life into an aging machine. It is not intended for a new high-end build, plain and simple. If you are building a high-end machine, it would make much more sense to get a decent size SSD drive and make it your primary OS drive. You will see the best performance that way. I suspect if you have an older 5400rpm SATA drive and aging hardware to match, it could really benefit from the HDDBOOST. If I were to use it in an existing setup that I did not want to reformat, I would get a 30 GB SSD drive which you can pick up for less than $100 these days as opposed to using a larger 60 GB that I tested with.
If budget isn't a concern or you need 100% SSD drive capabilities, I would recommend getting a 60 GB or larger SSD drive and skipping the HDDBOOST. Yet, once again it is important to note the HDDBOOST isn't trying to fill that niche. The HDDBOOST is marketed for older systems where the user wants a speed increase without having to reformat their drive.
I have no problem giving the Silverstone HDDBOOST the OCIA.net Silver Seal of approval. It is a unique product that fills a very specific area in the market between legacy technology and modern high-end equipment.