I've had her sword since I was level three, now I'm level 41. Other than the fact using her sword will fll all the empty soul gems you have in your inventory, Is there any reason not to return it to the shrine?

Nope...
'cepts its a really strong weapon...

Always opted for the "Honorblade of Chorrol" over Umbra at the very start of the game because my low level character can repair it. Even then that sword becomes instantly obsolete with access to the enchanting alter. I spend nearly all the game, after around level 10, quite happy with an enchanted Dai-Katana.

The weapons the player can make at the enchanting alter are so powerful they have been called cheat weapons in the past. We're talking about killing a level 41 goblin warlord (1,230HP) in 5 seconds kind of powerful.

It makes for a superb sneak attack weapon because its base damage is so high and that's all that recieves the sneak attack damage multiplier.

I agree however that the enchantment is sort of like a self-licking ice cream cone. :tongue: