I learnt a lot from him: not only how to write concise English, but also the way to think in English. The guy is awesome. Personally, I like his style: strict and blunt. He will never flatter you but you got the REAL improvement.
During the work, Sandy is always strict and sometimes frustrating, but I personally like it because I know that’s the way to make results.
As to H/W/S I would rec. SK for the following reasons to the following people:Big ideas and excellent execution for HBS package. SK is good for guys who can think. If you use SK, be sure to be inclusive and work hard. He doesn’t write for you