Obviously it cannot be faster than a local DNS cache/server (for the RTT). What can be significantly faster is forwarding queries to Google Public DNS instead of your ISP. At least in my experience, ISPs often have slow and overloaded servers which are not well maintained. Recursively resolving completely on your own is often even slower than either of those two choices.
I have been running unbound for a month, and there is no noticeable difference in resolving time. This article provides a good read: http://linuxmafia.com/~rick/googledns.html
