I've never supplemented regularly but do have a litre of choc milk, half pre and post workout.
The information in the link above makes me feel a little better about taking it now.
I want to supplement in the future and keep it simple so need advice. Energy levels, strength, preventing muscle soreness from increased training and protein. That's all I really need and to be honest I don't get a lot of muscle soreness at all once I'm 2-3 weeks into a training cycle.