I've heard great things about Dr. Giesser from someone who studied under her, although I've never had the pleasure of meeting her as I'm near NYC.
The first specialist I saw was Dr. Aaron Miller at Mt. Sinai in New York. He's very good, and is one of the most well-regarded/respected MS specialists in NYC. He definitely knows what he's talking about and made me feel very confident about the treatment I would receive.
About a week after seeing Dr. Miller I had an appointment with Dr. Saud Sadiq of the International Multiple Sclerosis Management Practice (they also have a research arm called the Multiple Sclerosis Research Center of New York).
Dr. Sadiq is one of the nicest people I've ever met. My first appointment (as well as my second, my third is in January, though I've been able to speak directly with him on the phone whenever I've needed to) lasted a little under three hours. The first two minutes were spent with a nurse, who was getting all the basic stuff done, blood pressure, weight, etc, but after the blood pressure Dr. Sadiq walked in and said he'd take over and I spent the rest of the time with him.
He really cares about his patients as people, not just as their respective illness/symptoms. We even spent time talking about my personal life, and he gave me some good advice on it. But the main thing is how dedicated he is to his patients, as well as finding the cause and cure of MS (he still handles research as well as sees patients).
The wife of a friend of my father's has MS as well. She was in the hospital for a particularly bad exacerbation and that's when they found Dr. Sadiq. He told her that he would be with her every day until she got out of the hospital, and he was, didn't miss a single day and didn't just pop his head in, but spent time with her. I know that for her, he's made a huge difference in the disease (she has SPMS). For me, he helped me out of the really bad place I was after my diagnosis.
I know, I'm going on and on about Dr. Sadiq, and I do think he's the best doctor I've ever met, but I don't want anyone to think that Dr. Miller is anything less than an excellent doctor and one of the best MS specialists in the area. You can't go wrong with either of them.
One last thing--I think the reason you see a specialist is that the specialist has spent so much time with MS, knows it so much better than a non-specalized neurologist, may be able to see things coming, and definitely keeps up with the latest research and trials going on. Personally, I'd rather see a doctor who dedicated his/her career to MS than someone who might see a case of it a couple times a week, if that. That said, if your doctor isn't willing to listen to your opinions, then it might be time to get a new doctor.