I think the OD&D rule of dividing dungeon level by PC level (to a maximum of 1) to get the XP multiplier that a poster above mentioned may work well for
4e and prevent rapid levelling from 'grinding' easy fights.
So eg, on the 1st dungeon level the average encounter level and treasure packet are 1. A 2nd level party on the 1st dungeon level gets 1/2 XP for encounters, because of the reduced risk. When they go to 2nd (or deeper) dungeon level they get full XP.
I'm not sure this is necessary for
3e, where XP needed to level initially escalates rapidly, but might be necessary from 4th level onwards since CR 1 encounters are still giving full XP per
RAW 3e while no longer being much threat.