Considering when we're seeing this release very little was expected from it for the simple fact AMD offered us such a huge driver last month in the form of the 11.4s. Unless the HydraGrid improvements are something you really want or one of the bug fixes impact you directly there's probably not a whole lot of reason to jump across to this driver.
On the performance side of things it's a little wobbly with performance going a little down in some areas and a little up in others. It's not really enough to probably sway most people one way or another. Instead it's going to be more about figuring out if the bug fixes or HydraGrid features help you.
The 11.5 isn't a bad driver and if you're just buying an AMD card today you may as well update to it, if you're on the 11.4 driver set, though, you're probably better off staying on it because if it ain't broke why fix it.
For now we'll be sticking with the 11.4 driver just to make sure everything is consistent in our own testing. With no real key performance differences either it won't impact the decision of how we rate any video cards against NVIDIA.
With the normal array of bug fixes and some improvements to HydraGrid, the 11.5s aren't a bar driver, if you're on the huge popular 11.4s, though, you may as well stay there as it's one of the best we've seen in a long time.