The very folks that Femtocells will most help, are SOL. Face it, if you are so far from a cell tower that you don't have a good signal, the chances are that you are beyond the reach of DSL and Cable also.
I'm 5 miles from the phone switch. Unless they put a DSLAM in the junction box in my driveway, DSL will never be here. I'm also 3 miles from the end of the cable line. Jetbroadband mumbled something about the next 12th of Juvember after Hell freezes over before they extend the cable line.
So, I'm on a satellite Internet connection. VOIP is very, very poor over satellite due to the latency issue. (Minimum ping time is in the order of 650ms or greater.) A femtocell repeater connected to my WIFI would be useless.
Less than 40% of US citizens are connected to broadband.