depending on how the water is carbonated, the sodium bicarbonate gas is also a neutralizing agent for lactic acid so it may be that carbonated water may not only be absorbed faster and can also help neutralize the nasties postride.

I love my soda stream- I also like the camelback tablets that are carbonated- I just use them in my sports bottle with a combination of frs- delicious and doesn't get as funky tasting warm as some other combinations.