Don't you guys think that even in Master Difficulty Sneaking is veery easy?I know if you are a high level you are hard to detect,but even if you sneak in front of a person you may remain "Hidden" and if you are in the middle of a market place and sneak,you may remain hidden,I think they should Improve Sneaking...But only in the nexts ES games...

http://youtu.be/lHbF9ynGZV0
Skyrim sneaking in a nutshell

When you can stand right in front of someone and remove all their clothes and they don't notice ... yeah, it's ridiculous. I generally only perk Sneaking up to get the archery damage perk and that's it. The rest are just way to over the top IMO.

I always wonder, maybe they should add certain enemy type like spellsword or mage that use detect life spell against sneak.

it is a channeling spell so they won't cast it constantly, but when on alert mode they will cast it. once cast, you will be instantly revealed even you are in invisible mode.