Spoilers:

Hello everybody,

So, finally, after much sweat I was able to acquire Master Lockpick level for Sly form Rukh in Red Light District. Problem is - how do I use it? I´ve thought it will make game easier for you, but it seems it doesn´t.
For example, I wanted to lockpick chest in Sly´s room in Rowdy´s Bar, because I´m curious what´s inside. Problem is, even with Master lockpick, lockpicking itself is equally hard as without it: Three or for lock pins and only 10 second to open them.

I´ve thought Master Lockpick skill will make it easier on you (fewer lock pins/ longer time), or am I missing something?
Am I using it correctly?

I just came back form Hephaestus and I was told to go to Limbus. All my characters now have the master skill, except Stilletto and one unrecruited character.

Help would be appreciated.

Bolch76 is correct. What the master level skills actually do is allow you to pass certain challenges that are impossible otherwise. There are certain locks in the game that simply cannot be picked without being able to reset the timer, and similarly there are people who can't be jabbered unless you have Master level, and similar situations for the other character skills. Obtaining master level lets you get past these challenges, and it usually means returning to places you've already been to track down those parts you couldn't access before.

True, but most of the backtracking is entirely optional.

Yup, but without it, it´s just a half of an experience it could be :)