It would be crazy to say that you're going to feel the benefit to taking these products. I suspect you would only notice a change if you had severely depleted your glycogen levels. I'm no expert but I think any sports scientist would agree that these products are to be used to top up your glycogen level.
Having said this they gave me no gastro issues. Of course they are crazy expensive but if you are serious about your sport it's not something to scrimp on.