Before Blog@Case went into Open Beta, I wanted to have finished the Create/Edit Wizard that would allow easy changing of a blog's look and feel. Alas, though, it is still in a partially complete state and has not been released.
But, looking around the Blog@Case system, I see people have already been reaching in to the XHTML and CSS and personalizing their site, which I think is great. Ben's modified his to look like the standard Case template (which www.case.edu/its borrowed). Cool's blog has a really nice green theme going. But, you just have to check out Brian Beck's Blog. That's a seriously cool design he is playing with.
Let me take this chance to apologize, I know what a pain it is to change the templates on this system. I had really wanted to have had the wizard done, but I didn't make it by the deadline. But, it will get finished. If anyone out there wants to use some of the styles from places like MovableStyle, you can; however, it takes a couple of steps. First, you need to reset all of your templates to the Movable Type default templates. That means deleting all of the current one's. Then, you go to Movable Type's default template listing, and you have to recreate all of the templates via cut-and-paste. Once you have done that, you can go to their default stylesheet listings and pick up some new CSS.
Yes, I know how much that sucks. Yes, I'm sorry. In a couple weeks (hopefully), the wizard will be done and it will automate all of that.
There are, also, crazy things advanced web designers can do on the Blog@Case system, which involve linking all of your templates and stylesheets to files; then use WebDAV to mount your blog's web root; and modify those templates with Dreamweaver. All of that needs documenting, though.
Lots of documentation still to do. Trying to get the system to the point where all of the things that should be easy are easy, and all of the hard things are, at least, possible.