I don't seem to have much luck sneaking when invisible. In Oblivion, you did not need to sneak in order to remain undetected. I seem to almost always get detected. I would think someone above level 50 in sneak would be unseen if invisible by some Thalmor guards at their embassy at night. They seem to find me with little trouble. It seems as if invisibility is like the chameleon spells in Oblivion and Morrowind.

Are you wearring plate armour and not using muffle?

If so that's your problem right there... you might be invisible but you're clanking around like a bag full of tincans ;p

I use light armor only. In previous games, invisibilty was all you needed to use to be undetected by anyone not able to detect life. Now it seems you are kind of invisible depending on what you are wearing and who you are trying to sneak by. I wonder why they did away with the chameleon spells.

Get the silent casting perk or invisibility is useless, also get muffle use them both.