We just noticed an issue today with some links we had on our Force.com site where some links to download some PDFs (stored as Documents in SF) were broken in our test environment (Winter '14) but not on production (still Summer '13)

The code looks something like this:

<apex:outputLink value="/mySite/servlet/servlet.FileDownload?file={!formPDFId}&oid={!$Organization.Id}"
styleClass="standard-blue-button" target="_blank">
{!$Label.lnk_PrintConsentForm}
</apex:outputLink>

In production, the link is fine, but in our staging environments, it seems like Winter '14 is automatically adding in the site prefix, even though I didn't ask it to, so I end up with /mySite/mySite/servlet/....

Anybody else experiencing this? Didn't find anything in the release notes related to outputLink or site prefix.