I'm also aware of Samuel Allen in Durham, and Lori Oshrain in Efland. I expect to use Oshrain for my second surgery letter.
I am/was* a patient of Kimball. The only complain I have about her is that she will not refer clients to anyone but Dr. Holt for HRT. I learned this because I was having problems with Dr. Holt (she was basically unwilling to prescribe to me but did not articulate any medical/health reason for doing so) and asked Kimball for a referral to another doctor, which she refused to do. If you are like many I know who never had difficulty with Dr. Holt this won't be an issue.
* Technically still am, but I've only seen her twice since the start of 2011 as I'm at the point that there's little to cover in the therapy sessions. She ended the last one by telling me, "it seems that things are going very well for you. Call me when you need a surgery letter."