The USGBC commissioned a study that concluded there about 25% of LEED buildings used as much or more than a traditional bulding. That was deemed to be a bit of a problem--on the one hand, 75 percent of LEED buildings do better, but a full quarter of LEED buildings perform, at least energywise, the same. The USGBC realized through that study that a few different things were happening. First, there was no requirement for ongoing commissioning assistance--your HVAC system may be great when you first install it, but without proper maintenance it will underperform. The new LEED requirements call for ongoing commissioning.
The second thing to change is occupant usage. You may have daylight sensors so the lights go out when somebody leaves a room, but if occupants don't know how to use those features, your energy savings won't be there. If you have these systems in place and people show up and plug in their personal space heaters, you're going to have more energy usage than the projections had shown.