IMO they are the best and I've suggested them to friends. Dr. Mark is blunt and to the point and some people seem to feel his bedside manner isn't touchy feely enough. He's more like a doctor or surgeon than your typical vet which frankly is what I like though other people might take it as chilly. His own dog comes to work with him and you can tell he loves animals. He's in between cheap and expensive but he itemizes everything first and the time my cat had surgery he asked "Is this OK?" and I got the feeling if I had been poor and my animal was in need that he might have worked out some arrangement with me.
I took my elderly cat to him three years ago to have a tumor removed and the experience was similar to going to a doctor for humans which is good because to me she's like a human. He took things seriously and was honest with me. I didn't want things sugar-coated and I wanted to discuss her situation frankly and know all the facts. He handled everything from the X rays to surgery to making sure I understood how to give her pain medicine. They do bloodwork before any anesthesia and Dr. Mark did a beautiful job removing her tumor (which was behind her ear and a difficult place to operate ). They never release any animal until they have recovered from anesthesia and the staff is sure they are OK. He called me personally after surgery to let me know the labwork showed that it was a slow growing tumor and you could tell he was happy it hadn't spread. 3 years later my girl is 17, tumor free and running around.
If you want to go to a cuddly vet with cute posters in the office who spends all day with puppies and kittens and will tell you that it's just time for an elderly animal to be put to rest then go to any of the busy, cheery vets in gentrified nabes like Park Slope. If you want a serious doctor who knows that it is the animal not the person who is the patient or if you have an older animal or one needing serious care or surgery then Dr. Mark is your man and he's worth a trip from other neighborhoods.