For $80, the Addonics ADCBSAR5-2E does exactly what you would expect: It gives you the option to add high-performance external Serial ATA storage to your notebook. Simple hard drives or even storage appliances based on multiple hard drives (as long as they have a built-in RAID logic or port multipliers) can be connected. Unlike USB 2.0, setting the card up will require the installation of a driver, which shouldn't be a problem.
Write performance was a minor disappointment, but read transfer rates exceeding 70 MB/s are more than just acceptable. These numbers are good enough to outperform any USB 2.0 storage device and most of the Firewire drives we've seen so far. If you're looking for a way to hook up high-performance storage to your notebook, Addonics' CardBus adapter is hard to beat.
You might ask yourself why people would need high-performance storage for a notebook, and the answer obviously lies in application requirements: If you do a lot of photo editing, video, audio processing or similar applications that require a lot of data transfer from the hard drive, having a fast storage solution will make one hell of a difference. Notebook hard drives offer data transfer rates of between 35-55 MB/s, and performance decreases significantly as you fill up the capacity. I would want the write performance to be improved before buying this product, though.