Im pretty sure that nothing except for acrobatics and athletics are affected past 100 skill wise, and im sure the same would apply to attributes as well
You are right about skills but you're wrong about attributes.
Most or all attributes have benefits above 100.
Strength - More Fatigue (aka Stamina) and increased encumbrance limit, but no additional weapon damage
Agility - More Fatigue, unclear about affect on sneak, lockpicking and staggering
Intelligence - More magicka
Endurance - More health and fatigue
Willpower - Faster Magicka regen, except for Atronachs of course, and more Fatigue
Speed - faster movement
Personally - Maybe a higher disposition, but it doesn't matter much
Luck - over 100 affects some misc things like Mehrunes Razor and Arena bettng