Details:
I live in the Shenandoah Valley just outside of Grottoes VA. My internet is via Sprint using a (portable) pocketWiFi device that "beams" my internet from a tower located far away. I went with Sprint since they have an unlimited data plan (which I formerly had with Ntelos, which was bought by Sprint). I originally had only 1 bar on my Wifi device, but after chatting with folks at the 3G store, they recommended this product.
I was skeptical, but took the leap. WOW! It worked great. You get a booster, an outdoor antenna, and an indoor antenna. The outdoor antenna collects the signal, which is sent to the booster and then to the indoor antenna; the boosted signal is then sent to my Wifi device, which sends the signal to the rest of my house. I have consistently 5 bars. I am really impressed.
A few things to note: you will need two people to set this up; one person to manipulate the outdoor antenna (that is hooked up to the booster + indoor antenna) to find the sweet spot for the signal, and another person inside to observe the Wifi device to see the difference in signal strength. If you have a portable Wifi device that runs on batteries (as mine does--it also has an AC adapter), then just take the device outside/on your roof and look for the signal change. Once you've found the high-strength area, that's where to start with placing your antenna.
Across the board, this was a very successful purchase. The folks at 3G store were great, and they even followed up with me to make sure I was satisfied. Great product, great business.