As of OFP version 1.20, BIS enabled joystick support for control of vehicles in the game. However, there are some quirks in the support that can cause some not-so-pleasant side effects if you don't take preventative measures.
Some people have reported OFP stuttering, lag or freezing up every 3 to 5 seconds. Others report that their screens looked as if they were shaking their mouse rapidly left and right.
This was caused by their having one or more joystick or gamepad controller devices defined under Windows Control Panel's Gaming Options but not having one of those devices physically connected to the PC when OFP is started.
The solution is to either have only game controller device defined to Windows and connected before running OFP and/or to remove all non-connected game controller device definitions from Windows Control Panel's Gaming Options before starting OFP.
Even if you don't have any of the above-mentioned side effects, if you've got more that one gaming device connected to your PC, you'll only be able to use the first one listed in Windows game controller list.