MS recommends disabling auto-create statistics on SP DBs (ref).
What about auto-update statistics?
Looking at our TFS installation, for the SP DBs, these two options are disabled for you when TFS is installed/configured.
SharePoint runs a daily timer job that updates the statistics for you for a number of databases. It also checks the health of your indexes.
You can find more information in the following article: http://technet.microsoft.com/en-us/library/cc262731(v=office.14).aspx