I have a Wilson cradle type booster with their directional antennae. I would consider it one of the most basic of boosters and it dose improve signal strength but it's a kin to fishing. Sometimes it really helps but it's not a guarantee of signal. The biggest challenge of Cell signal in back country is that the networks antennae on the towers are directional and are "faced" towards the areas of land that have the most cell phones. Example, in a city antennae are arranged in a somewhat circular (triangle, square) array because there are people in all directions. When your out along a major highway they are arranged parallel to the highway and often none are positioned perpendicular. So if your boon docking 90 degrees of the highway, and only a few miles away, there will be zero signal. My booster doesn't help in this situation.
Where my booster helps the most is boon docking a few miles from a city or town (signal eliminating in all directions) where I have the tiniest of signal, say -118dB and I can occasionally text but no data or voice. Often once I've acquired the direction of the tower with my antennae and booster I will have good enough signal for data and voice. I'm not sure why, but the booster also helps when there is a lot of cell traffic. I have found that in the middle of the night I don't need the booster for data but once morning hits when everyone is on their phones I loose signal. And then the opposite happens in the evening. The booster often helps with this as well.
I carry my booster as a tool that is available to me when "out there" but like others have mentioned it's not a perfect solution.
-Eric