I use ik when I need to keep the hands locked to something that is itself fixed, like say a ballet dancer holding onto the practise bar.

I found that using the dials to move the hands or feet works best and slow movements  to allow the IK calculations. you may in some cases need to dial in the bends of the collar and shoulder if the limb looks unrealistically bent. same for legs. turn in or out the thigh. 

Extreme positions will move the chest and hip.