Take it into your local Apple Store and see if they can reproduce the problem. You're still within your 14-day "grace" period, so you could always exchange your MBP-R for a new one, or return it for a refund.
It shouldn't be running anything slowly. Unless it's something with your wifi connection when you use Safari. The Apple Store has their own widi set up and can test Safari as well.
Try going to the Safari menu and select "Reset Safari..." The default check boxes are usually pretty good, but uncheck anything you are uncomfortable clearing out.
I love the way safari renders text (even before retina), but its terribly slow compared to other browsers. I find that I have to constantly clean out stuff and restart to make it useable. Generally I just use Chrome.