For the slang word "gonna" it suggested this to help correct the error:

"i before e except after c or when sounding like A as in neighbor and weigh."

It does offer up some good suggestions, but just like Word and most other checkers, it's still too stupid to understand what it is you're doing and will still suggest you do things that are just blatantly incorrect. You still need a grasp of grammar and usage so that you don't make ridiculous mistakes based on what it thinks it's found. Thus, it throws every rule that I don't know in doubt when it suggests them, because if it's wrong about that, is wrong about this too? It did find some things that surprised me I over looked so bonus points there, but it's very slow, you constantly get the beach ball of death waiting on it and in the newest Word for Mac, it doesn't actually correct the text, I have to make the changes by hand as I follow it along... so what's the point?