With Rod's recent 100 Permas, I wondered if you could possibly get stacking benfits from leveling. That is, level up, have xp drained until you level down, then level up again.
Just gave this a quick test, and it doesn't. Not really. You do not get free skill points. You do not get more HP. You do not get bonus stats. It's as if you had never leveled... except if you've spend the skill point you get to keep the skill. Not that that's at all viable for anything past level 1 at the moment.
You can however effectively do rerolls of your level up bonuses. Mage's INT decreased? Drain a level and try again. Maybe it'll go up this time.
You'll need to just barely make your level if you do this. I'd recommend doing low xp monsters/quests as soon as you get close, otherwise you'll have a long time waiting for the xp to be syphoned off. You will level much more slowly as a result, but you will get better stat increases.
Disclaimer: If you get your main character permakilled while doing this, it's not my fault! XP drain, as the game constantly tells you, will destroy your character if you lose all your xp.