Hi Przemek,
It is a bug, I tried adding your setting on my local machine using MS SQL (its not a db specific issue), and got the same result.
The problem was if the user property had never been saved it did not display the property, the fix was to show the default value in that case.
So, in other words if you save the user profile after adding the setting it shows up on ProfileView.aspx but if you never saved it yet then the user property is null and it was not showing anything.
I have fixed my copy and will have it fixed in svn trunk soon.
Best,
Joe