How good is the nutritional tracking on MFP??

Hi Guys,
I've been using My Fitness Pal on my iPhone for several months now and have found it very useful for tracking my calories so as to let me maintain a healthy weight. My question is how accurate is it at tracking nutritional values of various foods?

I was having a look at my weekly Nutrient Details and noticed that my Potassium level has been ridiculously low over the weeks that I have been using the app. For example last week my total intake was shown as 2,652mg out of a suggested 24,500mg while the week before showed 3,378mg out of a suggested 24,500mgs! Could this be right? I am pretty sure that my diet is fairly healthy so I’m slightly confused as to how my intake could be so low?

Anyway I looked up the symptoms of low potassium online and many of them matched how I’ve been feeling over the last few weeks: Weekness, Tiredness, Cramping in arms, Tingling and Numbness, Constipation, Feeling very thirsty a lot of the time as well as feeling a little depressed.

Obviously I’m going to try to increase the level of potassium in my diet (I found a good link with some suggestions here: http://www.healthaliciousness.com/articles/food-sources-of-potassium.php) to see if that helps the way I’ve been feeling of late but I wanted to check on the accuracy of the app as I don’t want to go overboard and take way too much potassium as that might have other side effects.

My sodium and cholesterol intake seems to be below the recommendations also so I don’t know if this could also be having an effect on me also?

In your experience have you found the program to be fairly accurate in tracking this information?

Many thanks for reading

Steve