For those who own a d40: do you normally change the ISO/whitebalance/aperture or do you normally just use the auto setting? For those who own a xti: how useful is the proximity sensor? Is it really that necessary? As you can probably tell, it's b/w the d40 and the xti. I'm mostly interested in taking portraitures for my clothing company. I've tried both cameras out and they both feel natural in my hands.