I'd say that SC is the toughest area on the GMAT to get the most questions right. In the quant, you can at least check you answers in most cases, and often times there is more than one way to answer the question. This gives you a bit of fail safe.
In RC, the questions are able to be answered 90% of the time directly by wording in the text. CR questions if correct, are air tight. However on SC, you can never be 100% sure of your answers. Sometimes the best you can do is just narrow it down between two choices. This is even true for test takers that score 750+.
GMAT knows this and weighs the SC questions appropriately. You can get 5-6 wrong and still get a 40+ score, provided that you minimize mistakes in RC and CR. Also, in verbal it is imperative that you finish the section. Leaving a few blank will severely damage your score.
Be careful of hard and fast grammar rules... GMAT tries to make it seem like a sentence should follow a rule, when in reality it doesn't. For example:
Look how many people got it wrong because they thought a simple grammar rule would led them to the answer.
The thing that helps me the most on SC is realizing that in the wrong answer choices, most often, at least 2 things will be wrong. Take the previous example: the question is testing modifiers, and the logical meaning of the sentence. If you are focusing on just one aspect of the sentence and you can't get the right answer, try a different approach.
So... don't really worry about crushing the SC, it's extremely tough to do. Maximize your right answers in RC and CR and you'll do fine.