My general expectation is most girls wouldn't mind being rimmed but a lot lot less would rim the client.
I recon that's about right but then there are some mucky girls that no matter how many time you say no they still try and rape your ass... The more you refuse the more they feel like they want it. Before anyone asks I'm not naming names for this because IMO rimming is one of those things you have to find out for yourself, and for something like this what a girl does with one client may not be what she would do with the next.
Although I wouldn't allow it on me, some girls little starfish need to be kissed (getting dirtier as I get older).