You never know what lies beneath. Two great hotkeys in Visual Studio are [Ctrl-M-O] and [Ctrl-M-P]. The "O" one collapses your current definitions down to outlines. The "P" one expands all outlined definitions. The great thing about that is that you can quickly get a feel for
a) the properties, events, and methods of the class and b) the complexity of the class. When you use regions, you lose both capabilities.
Here is an example of collapsed definitions without regions:
And here is an example with some common regions:
No sir. I don't like 'em.