It would appear that Google+ could finally be catching on, if comScore's numbers are anything to go on. comScore has been released numbers that count how many unique visits a site gets. This means it doesn't take into account how long a person stays on the site or how many return visits that person makes.
But enough disclaimer, let's get into the numbers. comScore says that Google+ saw 110.7 million visitors worldwide in the month of June. Compare that to November of last year and the number is 66% higher. Furthermore, strictly US traffic over the same period increased from 15.2 million to 27.7 million, a growth of 82%.
Facebook, over the same period, dropped from 166 million US users to 159.8 million. In November, Facebook had more than 11 times the unique hits that Google+ had, but now that number has dropped to only 5.8. However, this is where the disclaimer comes in. More people may be visiting Google+, but it is likely they are still spending much more time on Facebook.