We have two cell phones for business in the US. They are invaluable.
Ever try to find a coin or card phone empty at an airport? I don't
travel w/o mine and neither does my girlfriend. We also have an
international cell phone that, because of protocols, does not work in
the US. Again, it has proved invaluable on business trips. Our US
service is a little flakey at the house as we are low and rural so we
keep a land line. My girlfriend's sister has a landline that is only
for local calls (and incoming) and uses her cell phone for long
distance.

I agree that people are a nuisance with them. Our phones, if on, are
always in "manner mode" when we are in a restaurant (buzz, not ring).
In the rare event we get a call, we keep it very short if we take it at
all.