>IMO, it doesn't matter as long as you're not holding your
>breath.
I agree. In fact, I picked up a tip from a Kettle Ball trainer who inhales on rowiing moves (for shoulders and back). That goes against the traditional recommendations, but I find it helps to stabilize the shoulder joint and keep the chest up during the moves.
I think the Valsalva manoeuver is riskiest for those who are heafting really heavy weights (ie: the gym-going guys who get all red in the face because they are trying to lift maximum poundage, and tend to hold their breath).