Learnerheart in the simplest words is a cheat mod, allows you to level very, VERY quickly. It makes game a lot easier yes, but on the other hand, you can note that the game mechanics of Lionheart itself spawn more enemies when your character level is higher and also when travelling through crystal teleporters your character will encounter more powerful opponents of much higher level.
Great Mod
It deserves a 10 even just for being the first successful attempt to mod LLotC. I've waited years for this. Hopefully there's still a chance that the game would grow to have an active modding community much like its cousin D&D games (esp Baldur's Gate 2). Please more of this.