I know that the values change when I change enhancements, feats, and gear as would be expected.  So, the math on them seems to be accurate as to what your character should be getting, per the stated effects on the items (excluding the known bugs, ofc).  And it's my understanding that these character sheet screens are how people find bugs where stated effects aren't WAI.

I have no idea if those numbers on this screen are actually being used by the game engine.  There are some that show you the dice roll and the modifier that are easy to determine if they are accurate:

Critical Hits
Saves and Skill checks
Attack rolls

Some, it is hard to tell.  Spell DC's, Spell Pen, Spell Power, melee power, sneak attacks, PRR are all examples of things where they just give you the end result.  They don't show you the math. 

The ones that do show the dice roll + modifier all seem to be accurate, afaik.

OK thanks.  With this game you can never be sure.. LOL.