I think it really depends on what the personal experience is. I'm working with a wannabe writer right now who is dealing with some issues himself. He presents himself as a professional in a particular industry, but if he spilled all the stuff he's dealing with his professional credibility (and his credibility as an expert in his field which is the basis for his writing) would be shot. He is better off keeping his personal struggles to himself and drawing on other expertise for credentials and credibility related to his subject matter.
And there can be the 'scaring off' factor too. Certain issues can translate into heavy hand-holding/rescuing/talking down off ledges/or damage control. Once an agent has committed to a person and their project, they are very likely to develop a genuine concern for their client and be willing to do what it takes to ensure everyone's success. But sometimes, to know all of that in advance might make someone reluctant to take the chance.
I think you want to get past the introduction phase to the genuinely interested phase before you reveal much more than the fact that you can write and you have a deep understanding of the subject matter.