We get asked this question a lot.
As always, the specific answer depends on your particular requirements. Nevertheless, based on our customer research and recent product CMS selection experience, we can generalize that SharePoint remains poorly suited for most external web publishing environments, even in its most recent 2010 edition.
In an advisory briefing for our Web CMS and SharePoint subscribers last week, we describe eight potential SharePoint weaknesses for public-facing website scenarios. To quote from the advisory:
"Many of these weaknesses can be mitigated through extension or customization, but....this could substantially increase your long-term, total cost of ownership, compared to other, more focused tools from competing WCM vendors."
Keep in mind that SharePoint's sweet spot remains document-centric collaboration scenarios. Of course, it's possible that SharePoint could prove a good fit for your website CMS as well, but you should not default to that choice (or default to any other), and instead undertake a thorough review against other WCM alternatives.