SerenaFairfax: Thank you. I posted here looking for experiences that didn't come directly from an assessor website, so your post is most appreciated. The reactions you describe match very well with what I have seen on the couple of assessors sites that I have looked at seriously, it's good to have those confirmed. I do think the money could be well spent ... if I can get the right person. One of my concerns is knowing how even (what I think are) very good books get very different reactions from people, so I worry that I might get an appraiser who simply can't stand what I've written. I guess the hope is that a true professional won't react that way (but I have difficulty believing that to be really possible).
Justin Nemo: Thanks for your post. My first book has been seen by only a relatively small number of people so far, but quite a wide range nonetheless - if I was part of a writer's circle or some such then perhaps I might have more options. What interests me in Manuscript assessment is getting input from someone with real experience in this sort of thing (the assessors I've looked at are also editors), it seems like a sort of cut-price way of getting any idea how close the manuscript may be to good enough - to get the sort of feedback/opinions that you can't really get from "ordinary" readers.