The film ranks fourth in the list of films that most frequently use the word "f#!$".
Sure enough, there's a list on Wikipedia of I don't know how many movies that most frequently used the f-word. (Casino is actually now fifth in line...someone needs to fix the Wiki page. Don't look at me...I don't want to be involved.)
I did notice the F-word a lot in Casino, but as I watched, I wasn't thinking, "Wow...they sure use that word a lot." I think it's so overused in everyday language anymore that I don't really notice it. Not to mention it's my word of choice when something has really pissed me off or I've been injured.
But then, I'm still not used to hearing the S-word on TV. TNT & USA shows use it a LOT and it's still jarring every time I hear it. Why would the S-word jar me, but not the F-word? That's weird, right?