I have notebook Lenovo Y570, Intel I3 (mobile) 2.2 GHz, GeForce 555M 2048Gb, 4Gb of memory. It's a very low FPS at all. I have 15-18 FPS (lowest settings) in the town like Zelenogorsk and 15-17 FPS in the Chernogorsk or Novoselki.
I set the lowest graphics settings and I almost never receive the 25 FPS even in the forest.
For example, I can play on this notebook in games on the UE3 on middle-high settings with FPS more than 30.
In the mod I had 25-30 FPS minimum in the forest and 20-25 FPS in the cities on the good server. Settings was lowest too.
P.S. Also I have only Samsung SSD 840 pro if it can help.