So I finished Nehrim... As stated before, it is a very impressive mod. That some guys in germany made this for free and with passion, shows.
What really grinded my gear, was the crashes all the time ( the final battle ended with at least three crashed before I bite the bullet and changed it to medium in settings) and that took away the enjoyment of the game for me.
The game shines in the world and the exploration. That in nearly every dungeon you visit, you find a magical artifcat, some spells books etc, make it very fun to just run around in the world (the nearly 120 hours I spend, I spend around 90 of them just fucking around)
What the games lack, is in the Main story and side quests. The main quest line I never really gave a shit about and it never felt like that my character had any real input in what happining ( I never really understood why the lighborn were bad) and there weren't any real side quest.
I am now going to try out the followup, as I have heard it improve in everything that Nehrim were lacking in.
That it is now using Skyim instead of Oblivion, make me think it will be more stabil ( even after I installed the four GB ram patch, Nehrim crashed all the time).
So in my conclusion, I would recommend Nehrim, but be warned, it will crash.