I just had my interview with Donna LeCourt--it went, I think, quite well. She's an easy person to talk to, certainly, and she seemed genuinely interested in what I had to say.
The main piece of advice I'd give (if it's not to presumptuous?) would be to make sure you have questions prepared for her. She alloted a significant portion of the interview to fielding my questions about the program. If I hadn't had any, the interview would have been over in less than 10 minutes. As it was, we talked for half an hour.
Best of luck! As every day passes and I still haven't heard from 6 of my schools, I'm beginning to think of myself, already, as a future UMass student.