Gatorade tastes salty. The fact that you need to dilute it to achieve an isotonic solution tells me that in its undiluted form it's saltier than blood.

Personally, I try not to head out with just water. I figure there are other things that I'm using up besides water, so I should have some sort of sports drink (be it an -ade or just good old OJ & H2O) to replace some of that. This only adds weight to that rule of thumb.