A question for anyone who has used prereaders.
Do you get any benefits less related to textual changes? Winnowing down/understanding your target market, for example? Even if you aren't doing more external marketing, I'm wondering if this could impact integrated marketing concepts like cover art, the title and/or various descriptions to help you appeal to the right folks. Or, anything else.
It isn't a process I've ever engaged in. I've got at least one person I'm considering asking to preread my first work, but I don't really have a coherent rationale for the request, or more importantly, a good idea of what to ask for out of the process. VS's description of what he's looking for in the first post isn't as applicable for me, but my instincts tell me there might be some extratextual benefits.
I'm just trying to think it out.

Any input is appreciated.