There's no way going around it: this "mod" is better in a lot of ways then Skyrim itself.

If you have Skyrim, there's no reason why you shouldn't try Enderal out. The story, the characters, the quests, the world, the music are all spectacularly made, on the level of quality you would expect from the best AAA games. But this is a free mod, made with the love and care of indie developers.
The changes to the RPG systems are great in my opinion, but not everyone likes it.
I cannot imagine (and wait) what this studio could do if they weren't resticted to the base game's engine.

Seriously, play it, it's awesome.