We bought the WeBoost cradle for our down east loop trip. Our boat really isn't big enough (36') to give sufficient separation for a rebroadcast-type system, especially since we'd need it both on the flybridge and down below.
The cradle was often able to pull in a signal where the phones alone couldn't. We tether the phones to tablets and laptops.
What surprised us the most was how seldom we needed it. Throughout Quebec, even out on the Gaspe penninsula, we usually had a good signal with our Bell Mobility Canada plan. Only in far Downeast Maine, Eastport to Jonesport, was our US AT&T service spotty. In spots we had no signal, and in others we got a poor or intermittent signal even with the booster. But without it, we'd have none at all in those areas.
Overall, it was worth the investment, but it can only boost the signal if there IS one to begin with.