I don't offer it at work but I love it in my personal life. It's quite odd, my husband had a small/average dick and yet anal was painful sometimes, yet my subsequent boyfriend was HUGE and it never hurt. Perhaps for me this means it's about being very turned on, and also very trusting. I'm rarely turned on by clients, nor do I ever fully trust them, so I don't like to do it with them.
Also loads of lube and the right position - I find it more comfortable to take in missionary than in doggy.