I agree and disagree with @Ben414. If there are people whose research you're interested in, that probably says something about what you want do with your career. Picking faculty to study under is important because they have the skills that you need to conduct similar work, and likely have connections in your field/ area of interest. Even as an undergrad, I developed a close mentor-relationship with my advisor because I was interested in the same things he was researching, and I now have a pretty extensive understanding of his subfield - which has helped me shape my future. Then again, I am hoping to get a PhD after my master's so i may just be thinking too narrowly.
The extent to which it is important when compared to debt burden, reputation, location, etc, might be less significant, but personally, I think its a pretty important consideration, regardless if its a masters or phd program.