Tried it; removed it. Why?
1. It doesn't check grammar, just some simple statistical metrics (short sentence!). For example, it did not flag "I took the Coke off the table and drunk it".
2. It flags the same error repetitively (short sentence!)
3. When it finds a sentence shorter than 7 words, it flags an error, over and over. (short sentence!)
4. It is set for semi-formal English only, and will flag either very formal or academic English, or informal, colloquial writing.
5. In short, it found none of the errors I hoped it would find. Mostly, it found the same *short sentences*, again and again.