I also prefer real lemons, we have our own lemon tree, so makes it easy. Also what is really good is orange slice in your water. And a great combination is to put some cucumber slices in your water with the citrus. If you are not a water drinker, this makes a really nice drink. I can drink a gallon. I have used real lemon when nothing else was available. But fresh is always better.
I don't think their is any negative of putting any citrus in water.