In my current game,it seems like there's a whole mess regarding equipment bonuses. For example the Night-runner armor "+2 stealth" bonus don't fully apply on my main character (just+1), or the bonus stays even when the armor is taken off with Eder. So far, i noticed that a lot of hats, bracers, amulets... share the same problems. Most of the time, the buff isn't considered. I tried with several types of objects on all characters, and results may vary from one to another.
In addition, there's an issue concerning hats specifically. The way it looks is always irrelevant (e.g. a mail coif that looks like a hood). Once again, it only appears with magic/special helmets, the regular ones look properly.
Note: I'm writing this after the release of patch 1.04. I don't know if the problem existed before.
(thanks for reading, i'm sorry for my english)