I think there are two reasons for which I have given a neutral rating, and I think they are valid and would use them again.
1. Where everything was provided as advertised, but for some reason there was no great excitement in the meeting. Possibly due to there being no chemistry bewteen us, or we were both pulling in different directions e.g. in a roleplay. This is not the same as the SP just being lazy or disinterested. It is probably down to communication and expectations, and for a neutral rating would have to be as much my fault as the SP's.
2. Where the preamble is good, and the SP is trying hard, but just isn't very good at the job. Can't fault her for effort, and is a nice person to talk to and doesn't rush me out the door. Really needs to find a different career, or take some advice from other escorts.
When I read a neutral rating from other punters, I pay particular care as to the +ves and -ves that led to that rating to decide if they are important to me.