A funny thing happened on the way to the release of Batman: Arkham Knight: The system requirements were changed. It's not a dramatic overhaul, but if you've got an AMD video card stuffed inside your rig, you'll probably want to give it a look.
The updated minimum requirements, noticed by Gameranx, are very similar to those announced a couple months ago: Win7/8 64-bit, Intel Core i5-750/AMD Phenom II X4 965, 6GB RAM, DX11, and yadda yadda. But the graphics requirement, which was initially just "NVIDIA GeForce GTX 660 (2 GB Memory Minimum)," now states that on the AMD side of the coin, you'll need a Radeon HD 7950 with a minimum of 3 GB.
More ominously, the update warns that "there are some known issues with the performance of Batman: Arkham Knight for PC owners using AMD graphics cards. We are working closely with AMD to rectify these issues as quickly as possible and will provide updates here as they become available. We thank you for your patience in this matter."
The response thread on Steam is currently
22 23 24 pages long, and while I haven't read all of it, there's a lot of unhappiness. Not just because of the change, which has left some lower-end AMD owners unexpectedly unable to play the game, but because of the timing: The updated specs were posted less than 12 hours before Batman: Arkham Knight goes live on Steam.
Update: AMD has released new Catalyst drivers optimized for Batman: Arkham Knight, which you can pick up here, or here for Radeon 300 series hardware. However, the download page notes that the game may crash during in-game benchmarking or when exiting, and that the screen may turn black or pink when changing the resolution to 1680x1050. Crossfire support for Arkham Knight also remains disabled, but will be re-enabled in a future update.
Nvidia has also put out a custom Game Ready driver for Batman: Arkham Knight, available here.