From Google's JohnMu (John Mueller), here's some confirmation of a practice I've been noticing over the years. If you are redirecting your domain root to an inner URL in order to serve your home page, then a 302 is the best kind of redirect, not a 301.
For what it's worth, a 302 redirect is the correct redirect from a root URL to a detail page (such as from "/" to "/sites/bursa/"). This is one of the few situations where a 302 redirect is preferred over a 301 redirect.
Google Webmaster Central Forum [google.com]
I've seen this in action and wondered about Google's preference. The 302 always seemed to help, not hurt. So now we know. Using a 302 helps to keep the domain root in the index, with the content ranked according to the target URL.
Thanks to Search Engine Roundtable
[seroundtable.com] for calling out this Google Forum thread.