I haven't installed 3.0.1 or tried this yet, so this query relates to my reading (or misreading) of the codex.
I understand that I can set up a multisite with a front page (mysite.com, but it isn't clear to me what ends up on the front page - I wouldn't want a wordpress.com type front page) and then blogs/sub-sites either as xxx.mysite.com or mysite.com/xxx.
What I would like to achieve, and didn't get the idea I could from the codex, is that mysite.com would point to the main blog (in my case football club's site) and then sub-sites relating to parts to the club (juniors, committee etc) would be at xxx.mysite.com or mysite.com/xxx (haven't decided which yet). Basically, I guess I'm checking that the front page doesn't have to be just a general page but can be one of the sites/blogs.
I presume I would easily be able to make any sub-site viewable only to registered users (eg the committee site only to committee members).
Thanks for your time.