Rated 2 out of 5 stars
I confirm that this add-on creates duplicates. About 21000 total in my case and between 2-10000/contact. I believe that this caused my Android phone to get so confused that only thing I could do was to reset it back to factory settings. So you are warned.
Before this it worked nicely though. If this specific bug gets fixed (for sure) I'll enable it again.