Argyle King
Legend
Double the XP budget of all encounters. DMs can, and should, scale encounters for their own campaigns.
Depending on the group, I've seen that method still get squashed by the players. ...especially at higher levels. That's what one of the DMs I game with did for a few campaigns. Obviously, it made things harder, but the group was experienced enough (and PCs are powerful enough compared to everything else in 4E) that there will still battles in which monsters would get killed before having a chance to do anything.
In particular, I remember the party bard using Mantle of Unity a lot; for at least (he had a few item tricks which helped get it back) a round each encounter, the monsters had very low chances of hitting. On the other hand, some of the PCs were capable of rolling single digits and still hitting. The newer monster stats helped a little, but part of the new stats also was the lowering of defenses for some creatures, so their higher damage values never came into play because they were killed before being able to do anything.