This has been posted on many other forums. I figure it's a good idea to provide some feedback for GOG's games, if anyone is having problems with them, so I copied it from Anandtech's forum. Original post below:

Hello everyone,

AMD needs your help --

As we continue to improve our Catalyst Driver suite, we kindly ask you to help us by submitting any issues or bugs you have experienced with our drivers by using the form below. We value your feedback and intend to use the information you provide us to make our Catalyst Drivers better.

Note that this form, which closes on September 12, is different from the standard Issue Reporting Form we regularly use; therefore I ask that you use this form even if you already submitted to another form in the past. For the next 7 days we are making a concerted effort to increase the number of reports we receive to create a “bible” of bugs encountered by our customers.

Please click here to access the form.

Your feedback is greatly appreciated, thank you in advance!
__________________
Sam
Community Manager, Enthusiast and Component Channel Communications
Official AMD Representative

It's nice to see that they're actually trying at least. Because their driver really sucks, especially under Linux. Most of the games I have trouble running (and I mean the native ones...), well it's because of Catalyst...

Try to use the open-source driver, currently it works quite nice. I can even play Metro Last Light without problems.

More games have problem with the open source driver for me (very slow performance) so I'm stuck with the proprietary. At least it's been getting better with every release.

I have fewer problems with their driver than I do with the stupid CCC. Who ever thought it'd be a good idea to set every install default 10% smaller than optimal underscan?

has someone here already experience with mantle?