I am doing Kaplan private tutoring. My instructor is super. I am a non native English speaker. I have great math score. But my English really needs work. My first GMAT verbal was 15 which was only 8 percentile. After the tutoring, my second GMAT verbal score was 27 which was 44 percentile. (almost doubled). Of course, I am still planning to take it the third time since I really need 700+ score. The last GMAT prep practice exam I took I scored a surprising 760 with 50 in math and 44 in verbal. I would say private tutoring definitely helps. The only catch is that you need to fish for a great instructor. I tried out four different ones before I found my current one. I had to tell the Kaplan people that I am willing to pay only and if only I get him as my tutor.