oh yeah they definitely help w/signal issues, priority is SMS -> Voice -> Data and it often kicks you up a tier, so if you got SMS, the boosters can often give you voice.. and if you have voice, the boosters can often give you data.. usable data becomes the hardest, something like email can work as long as you let it soak and understand your on dialup speeds more than likely.. web browsing is hit and miss, and video streaming is an extremely rare luxury..
Its just many people think these work miracles, creating a signal where there is none to boost.. If there's a mountain between you and the tower, no booster is gonna make that work.. You still have to be hunting for locations that have some form of cell signal to boost.
In the next couple of years T-Mobile, AT&T, and Verizon are sunsetting the legacy systems.. I worry about whats gonna happen then, its very rare I find an LTE signal far away from any city.