Min supports IE5.5+, FF3+, Opera 9+, and Safari 4+, the best browser support of any CSS framework by far. Unfortunately, IE5.5 does not support border-radius and as such does not have rounded button corners. That said, IE5.5 users will be so surprised to see a site load correctly they will overlook this.
Min is extremely lightweight and doesn't prescribe a certain design for you, like Bootstrap. It's easy to override the default rules since there are so few of them and they are at low specificity levels. This customizability helps you avoid the Yet Another Bootstrap Site phenomenon.
Min uses the new HTML5 semantic elements liberally, has clear and short class names, and uses <div>s sparingly. Patients that switched from Bootstrap to Min reported up to a ninefold decrease in markup and drastic improvements in most cases of divitis. Ask your CSS-atrician if Min is right for you.