Experience required to level up now scales less exponentially (vanilla level 30 requires 1392 experience, with this feature active it requires about the same: 1395, BUT, vanilla level 100 requires about 31k experience while with this active only ~15k).
Experience is picked up faster
On death, players will drop 85% of their experience instead of at most 7 levels.
Ores and Spawners (or more generally Blocks that drop experience) will now drop 3x more experience.
Bottle o' Enchanting now give about 25 experience instead of 7
Anvil repair cap is increased to 1024 (vanilla is 40)
Renaming in an anvil is now no longer costs a level.
Mending is changed to reset the cost to repair an item back to 0, then it's removed.
Mobs spawned from Mob Spawners will now drop half of the experience than a normal mob would.
Since 1.18.2 experience from all sources is increased by 25%. Prior to 1.18.2: a config value is available to multiply any experience orb value dropped. By default the multiplier is set to 1.0 so nothing is changed.