I've always had very good luck with B&H and Adorama. I availed myself of Helen Oster's magic once. She/Adorama CS were fantastic.
If anyone is unaware of this.. Used Photo Professional is the used camera extension of Roberts. I pay a tad more for used gear at UPP. Every item is fully tested. Their rating system is way more than fair, and the have (had?) a generous return policy on used gear.