TerraDave
5ever, or until 2024
4E doesn't use an unqualified XP budget as such. Instead, it rates monsters as Solo, Elite, Normal or Minion, as well as giving them a level.
It's quite accurate for gauging the difficulty of a challenge. Each normal monster will fight one PC; an elite is 2 PCs, a Solo is 5 PCs, and 4-6 minions make up 1 PC. Level indicates the relative difficulty. By the XP budget, it might be fine to put a level 20 normal monster against a 7th level party, but because of the level disparity, it isn't fair.
I think the intention of 5E is that the XP budget replaces the Solo/Elite/Standard/Minion descriptors, while CR replaces the level of a monster. We'll see how it works in practice when we see more of the monsters!
Cheers!
MerricB basically has it, but to reiterate at its core 4E is really simple: a standard encounter is a group of monsters the same level and number as the party. 4 level 5 PCs, 4 level 5 monsters. You can add levels to make things harder, and 4E characters are tough, so you can add three or four if you really want to. Elites, Solos, and minions work as Merric noted.
Once you get the hang of it, it is really easy. But it is most easy when opponents are the same or a few levels higher then the PC. What 5E is trying to do is say "the ogre is always a challenge" wether a possible TPK to level 1, or killing a PC at 2 or 3, or a threat as part of a bigger group at higher levels. 4E doesn't do that well. Ogres can be a challenge, but they probably require some adaptation as the party levels, you can't just use the standard one out of the book over a wide range of levels due to 4E quite steep math.