Hi Jason,
Consistency is going to be key when formatting your sites URLs. If you choose to use 'www' or 'non-www' there is not a difference. Where people run into trouble is not using 'rel=canonical' in the tag to show the search engines that 'www.yoursite.com' goes to 'yoursite.com' or vice versa. If you do not have these tags in place the search engines will view the page are two separate pages, and you will run into a duplicate content issue.
So to recap, be consistent and use the appropriate 'rel=canonical' tag and everything should turn out just fine.
-Greg
