How do admissions committees evaluate coursework?
This is more of a general answer.

Graduate-level coursework should carry additional weight in a graduate school application, because it normally suggests that you are capable of doing work at a higher level than the standard undergraduate curriculum. However, it should be pointed out that more weight will be given to a full graduate-level course than a "shared" course that regularly offers both undergraduate and graduate enrollment. 

The primary red flag would be poor performance in one or more "core" courses in your discipline, while encouraging signs are taking more or harder classes and doing well in those.

As for the relative importance of this in an application, I'd put coursework in general somewhat behind the letters of recommendation and research experience. However, this is something that may vary from school to school, and even department to department.