I was told that 3G consume more energy than wifi; so I should use wifi whenever it's available. Is that true? Now, when the phone is idle (and both 3G & wifi are on), which one will it use? It seems 3G to me... b/c when I wake it from sleep, it seems to look for wifi again... So, does that mean I should turn wifi off during idle? Just trying to find a way to juice more out of the X!! Thanks.