Yeah, I don't get it how you can calculate the size of the label with a static method (NGUIText.CalculatePrintedSize), how does the system know all the settings on your label? I'm VERY curious about that. It must takes into acount the current font, the font size, the spacing of the label, etc...
Calling this method for me results in very weird results too.
But still, the printedSize accessor of the UILabel makes a lot more sense.