Although it technically violates the ATX2.X specs, I like single rail PSU's. With very few exceptions, total 12 volt output is less than the sum of the maximum output of each rail. And generally in the smaller (<1000 watt) PSU's, the rails really aren't separate at all.
Case in point: I have an Antec 650 watt TP3. It's supposed to have three rails with a maximum of 19 amps each. The ratings also say that the total max 12 volt output is 52 amps. And continuity and eye checks of the PSB indicate that all the yellow wires come from the same place.