and I have to say that I've had my share of disappointments both with porn stars and "normal" escorts. The reasons things go bad can be many and varied and there is no one right answer or solution. And I think, as a long time hobbyist, that for some of those reasons - the girl having a bad day, the me and her not clicking, etc. that there is no expectation on my part of anything to "make it right". Just like any date I might go on with any female, things just may not work out.
However, since this *is* a service hobby/business, anything the lady does or offers is, to me, a mark of a professional, and would certainly make me want to give her a better review than I might otherwise, or depending on the issue and circumstances, make me want to try again. One thing that I haven't seen mentioned as a possible offer if you don't click with the guy is to set the guy up with a friend (for free, or a discounted amount, or something like that).
As for tardiness, well, again, situations may differ. I've sat in my hotel room waiting for *hours* for an escort service to deliver. It happens. I think as long as you are in touch with the guy and let him know that you're delayed, it's ok. If something happens, like being on a shoot, you could offer to reschedule and any kind of "consideration" (additional time, discount on price, flexibility on activities or whatever) would go a long way to making the guy want to rebook. I think it's the not keeping in touch, that bothers people the most when you're late; and it works both ways - if the guy is running late he should be in touch with the girl to let her know.
One of the reasons I generally prefer to work with agencies is that if something goes wrong, they are more likely to do something to "make it right" especially if you are a regular customer because they want to keep your business. If things go wrong with an individual girl, well, there's no continuity, no expectation of keeping a customer and really the girl doesn't have to do anything although, as I said, it's nice when she does.