I have tried 2 different femtocells (from Verizon) over the years, both with only partial success. They "worked", but introduced bad call performance, and worse than that, much less than 100% of the incoming calls came through. The caller would either get a busy signal or it would go straight to voicemail without ringing. We pay for pretty good business internet here (Verizon FIOS Business 500/500), but after a ton of work trying different locations for the things, stopped using them.
Without the femtocell: Incoming calls almost always come through, but we get random call drops on all incoming and outgoing calls.
With the femtocell: Call drops are MUCH better, but only some of the incoming calls come through. Additional problems introduced with call quality - echos, 1/2 second delays, etc.
I have done tower-hunting with various cell phone apps in the past, but that map that
@YeOldeStonecat posted shows I have a Verizon (my cell vendor) tower .49 miles from me (it's the closest tower). T-Mobile is .52 miles to closest tower and AT&T is .79 miles to the closest tower. .49 miles sounds good, but Pittsburgh is not a flat place, there are lots of hills, so the topography is against good signal propagation.
Outside of my house, I get 2 bars of reception on each of the 5 separate phones on my plan. I've walked around the perimeter of the house and 2 bars is the best answer. Inside, it's 1 bar if we're lucky, and in the basement, between 0 and 1 bar, hence the poor performance.
I think the big problem is environmental - our office uses the entire basement of my home, which is built from stone, with plaster & lath walls on the inside... so lousy penetration on a good day. I have 4 APs in a 1,900 sq ft house. I don't know why the femtocells don't work as advertised, but after two separate attempts (@ $400 a pop) over the years, I'm done with them.
All of this is what leads me to getting an antenna for the roof and an amplifier. Expensive, but likely the only workable solution - at least I hope it's workable. That's the problem - I'm looking for some real-world experience with the things before I spend the money.