I've already commented on my peers and how they act at work, and I can assure you that putting them in khakis and a polo shirt doesn't make them professional. Personally I find it very easy to act lady-like when I am wearing the rib crunching, spine straightening apparatus that is often required for lady-like attire. When I am in a skirt I feel more presentable, and I am more conscious of how I am carrying myself. My professional clothes act as a regular reminder of who I am representing and how I am acting. This is because I like jeans, t-shirts, sports bras, and tennis shoes. I'm not always or necessarily uncomfortable in my professional clothes, but they are different. That difference is what works as a reminder.
I don't think nice clothes work as a reminder for our people the same way they do for me. Students are now dressing like this. If I was regularly in a mini skirt, my work slacks would be extremely comfortable. I think that if I was teaching, I wouldn't mind students showing up to class in their pajamas. Of course I'd want them to be attentive, but that is something I care about no matter what they are wearing. Pajama pants with pink flying elephants on them are novel and would probably get attention when they enter the class room, but a mini skirt and a low cut top is sexual and can be distracting for the entire period. I would rather they be in pajamas and learning instead of dressed nice and hooking up. This isn't meant to be a defense of all pajama pant wearers on all campuses. If you are unshowered and half asleep, that is disrespectful. If you focus better when you are comfortable, that is fine by me.
Despite my personal willingness to let students dress casual for class, I really like Paul Quinn College's new dress code policy. Having a university wide (or even program wide in the case of my Masters program) dress code means much more than a personal pet peeve of of pajamaed students. The change in clothes isn't going to bring about a magical change in student behavior. If it is enforced, it will become a physical representation of college's values and mission. It will be an indicator of what their goals are for their students and campus visitors will be able to see what they prioritize. Eventually, it would ideally work to only attract students and staff who have similar goals and values, but it wouldn't work to 'weed out' people. I think the dress code will do a great job of showing outsiders what this campus promotes. Clothes don't make the man, but they do make first impressions.
Edit: If you are interested, here is a story about the Illinois State Marketing Department and their new Dress Code.