I took a class under Ethan Todras-Whitehil and he's hands down one of the best teachers in this business. He's super funny and super interactive. He always stays back after class to help you out.

This course is pretty advanced so you do need some prior knowledge before coming in. Otherwise you can get up to date by doing the practice assignments before each class (its LONG).

This course is perfect if you have a 550-650 and you want to aim higher.

I immediately took the GMAT right after my class was over (without doing any further practice tests, etc.) and I improved my score by 100. Not bad at all. Can't wait to rally put in the time and see how it goes in a few months time.