Most pilots and controllers over here in the US say "one-two-five-point-five", although I do in rare occasions hear "one-two-five-decimal-five", and on some occasions, pilots will simply read back "one-two-five-five" and not say either "point" or "decimal".
As an aside, we have a flight out of here, American 2601, that goes, I believe, to STL. There has been a certain pilot that in the last couple of weeks (he's been here twice that I know of), has been answering as "American twenty-sick-oh-one". Sounds kind of funny on the radio.
Tom in NO (at MSY)
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina