Not much to 8.4.1 I'd say 98% was to patch the Jb that's why none of the bata releases had no notes . Really not worth it but won't hurt . TaiG has stated they will hold off until iOS 9 .
I like the Jb to change the look ever since iOS 7 the white / gray hurts my eyes (getting old) I never had any problems I run about 15 tweaks just have to watch the tweaks that but heads
Yeh they really need to give some options for night time themes etc. I used to use eclipse I think it was but not every app was textured/themed correctly (or at all)