The best solution is a good information architecture and menu system -- one that allows any page to be a comfortable entry page. Otherwise, you may send traffic from search engines to a page that may not clearly be on-topic for their search.
There are definite pitfalls. As noted, search engines frown on a fast redirect of any kind, and the site could be dropped from search results altogether. Counting on a referer to be there is also a problem -- see [webmasterworld.com...] for a discussion. Such redirect schemes also defeat bookmarked access to internal pages and the potentially positive viral effects of links in email and on other web pages.