I have always liked the fact that previous Zen versions had separate stylesheets fot layout, html elements, custom styles etc. More separation can also be useful, but downloading the latest D7 version was quite a shock to me. When the css directory of a fresh subtheme contiains 28 css files, I'm not sure where to start anymore. I'm wondering if this still efficient for my own and other people's workflow.
When I work with a team on a Drupal site, we need to know where we can expect certain css declarations. I'm afraid that too many stylesheets can cause confusion. Different developers can have different opinions about the right place for a certain declaration, or declarations that belong together will end up in different stylesheets.
I also think it's confusing that there is a large number of stylesheets, but only a part of it is enabled by default. New users may not immediately understand why editing a certain stylesheet has no effect. It may be more consistent to add only the enabled stylesheets to the starterkit css directory, and put the optional ones elsewhere. After all the templates directory isn't packed with example tpl's by default.
This is only my €0.02, based on a first impression. Maybe I will learn to appreciate it over time... I'm curious to hear your thoughts and experiences.