I like to think the school values it but I wouldn't say any more than having a great experience in anything else. For example, I've interviewed some candidates who have had wonderful research experiences and have been able to explain minute details to me (a good thing). However, I'd also say that a large percentage of students who say they do research do not really do much more then do PCR and run a few gels. That's not as impressive.
When applying to med school, it's more important to have a few experiences that you have pored your blood, sweat, and tears into instead of 10-15 things that you can't talk for hours about if given the opportunity.
Hopefully that made sense. I just took the boards and my brain is fried.