When I was recently on vacation I visited friends and incidentally they all lived just outside of smaller towns on the countryside. They all had a DSL line at home but mobile network coverage was weak at best. Apart from being a nuisance for me they said themselves that they were not happy with the mobile network coverage in their house. And it was not like they were living in totally remote areas. Perfect places for femto cells!
So while femtos haven't really made a big inroad in most countries over the years so far, I still see the potential and the need, especially since people more and more use their mobile phones instead of fixed line devices for voice calls. Sure, Wi-Fi and SIP clients could also do the trick on their devices when they are at home but it's not seamless and doesn't work for their guests. Fortunately, Vodafone seems to expand their femto solution to more countries beyond the UK now so let's see, perhaps that might be a solution for such locations and perhaps a reason for the competition to wake up.