I had exactly the same problem, and actually my whole mac was running a bit slow (<12 month old MBP 13" Retina, 8GB ram 2.8ghz i5). If I clicked to any webpage it would hesitate for a few seconds before loading each page. Google Maps was unusable.
I did:
Safari (toolbar) > Clear history and website date (all)
Safari > Preferences > Privacy tab > Remove all website data
Turn off computer.
Turn on, holding down shift. It takes a while and loads safe mode.
Turn off.
Turn on. It turns back on in regular mode, slower than usual but it gets there.
Try it after all that. It fixed it for me and made the whole computer is as quick as the day it came out the box. I guess it's because a mac these days never really shuts down/restarts even when you tell it to. By launching it in safe mode then restarting it seems to reset a bunch of stuff then it's happy again.
Apple... if you're reading this, if you could fix this problem that many of us are having on our $1000+ machines we bought from you, I guess that would be pretty nice.
Best of luck.
Chris
