Mine is hard to tell. sometimes it is rather accurate sometimes it is not. I remember using it to take a sunrise photo of the ocean a couple of months back and turn on the leveling thingy And I observe that the camera is asking me to tilt slightly to the right when i can see with my eyes that that will be moving away from being horizontal.
I did not pay much attention about it as I try to use my eyes to do the leveling. Where i fail, i thought to myself "oh well, try harder the next time"
The only time i really use the leveling feature is when i shoot at a low angle and do not want to crawl on the floor to look at the view finder. I then aim the camera at an angle and use the leveling feature to determine if the view is level or not.
Just like my iphone, the leveling feature is a nice feature but it is never accurate. if u really need that kind of accuracy, i suppose u can get those leveling spirit bubble thingy.