I've never understood the term "Pain in the butt"
 

I know what it is supposed to mean and it's origins, but from personal experience, most anal penetrations I've ever had have been pleasurable.

Do you agree?

I wholeheartedly agree. I've only had pleasurable experiences when I was fucked. My anticipation builds when I feel a cock against my bumhole. I want it in me so much that I start backing against it to feel the pressure increase until that moment when I feel the head slip in. At that point I like to hold still so that I adjust to the girth of the cock. Then I contract my muscles while simultaneously backing against my partner's cock. I want my partner at the same time to push deeper into me. I relax to feel the cock slide farther in and then I again clench. Each push feels more pleasurable than the last until finally I've taken it all in. Then my partner starts sliding in and out of me giving me more and more pleasure with each stroke. We fuck harder and harder until he's slamming his cock into me. And then comes the most pleasurable time when he shoots his load deep into me. I feel his cock expanding and spasming as he unloads.

Then comes the most pleasurable part. We don't move for several minutes as he keeps his cock in me. As soon as he's hard again we start fucking again. Unfortunately not everyone I've had has been able to stay in me after he orgasms, but it is oh so pleasurable when I have a partner who can get hard again without pulling out.

There's nothing like taking a load of sperm in me and then having it slowly leak out and run down my crack and onto my legs.

I'll take a cock in me anytime I can.

Anal penetrations are anything but painful---they are the greatest pleasure I have ever had !

LOT of LUBE and it works out fine!!

I presume most of the people using the expression (now as well as in the past) were not in to (or had no experience of) anal penetration :p

No

Pain in the butt, or arse isw a crude reference to the pain experienced from "piles" and has nothing directly to do with anal; penetration. However "piles" can be formed as a result of anal penetration.

Ive never understood the term "Pain in the butt"
 

If you are having trouble reconciling numbers and figuring out the equations, what hope is there for anyone else?