My only frame drop is in Zelenogorsk. It is a massive frame drop, making the game nearly unplayable in that city. However, along the outskirts (for example, the barracks) I have very little, but some, performance loss.

System:
Radeon R290 (4gb VRAM)
AMD FX-8350 (8-cores) @4.0GHz
8gb DDR3 RAM