I'll never get over Oblivion.
Does Nehrim require a custom UI?
Most of it is vanilla but it has some features unique only to Nehrim.
Most find that by installing Darn (or Dark Darn) over Nehrim that these unique to Nehrim features get obscured and lost.
JOG - has made a start with http://www.sureai.de/forum/viewtopic.php?f=86&t=3057 but it will definitely conflict with Darn UI.
Trying to recall what all gets disturbed ... loading bars, text on loading screen, Nehrim font (or whatever font they use), level up notices specific to Nehrim
It has some components of switching between graph and lines - I think kind of WZ inventory like. It has a kind of bunched up HUD, but many things are very similar. So I'd think an edited Darn UI would work and leave alone those elements above.
anyway - it is far more than a mod and is the first and complete total conversion - worth checking out especially considering the price. free