Edit: I did a little research on CDN resolution back in undergrad. One of the things that was most difficult to measure, or even define, was DNS "performance."
Just because Google anycasts its DNS network does not guarantee the best performance. Running namehelp on many machines I often found that the "fastest" DNS server was not in the obvious set of DNS servers that you use.
So I guess the answer to the parent's question is: yes, possibly, but it's hard to define what "fastest" even means here. I would say that jrockway's response is even incorrect in his (implied) definite assertion that it cannot degrade your experience. If you want to know, you should measure from your endpoint. There is no other way.
It told me my the fastest option for me was Dyn's servers, but those have unacceptable to me anti-spyware "safe mode" blockouts. #2 on its list was Google DNS which I was already using.
The graphs for HTTP performance said namehelp's choices were degrading my performance on average by 11ms.
Good app to add to the toolchest though. It'll be interesting to try it out when I travel.