I didn't know it was by a FTer! I use it on a daily basis and really enjoyed the group chats with my friends, and that I can keep my home number as a contact even with a SIM card with another number in another country.
TBH, I also use Line because the stickers are awesome and some friends use it predominantly. But Whatsapp is still my first choice for messenging because more friends are on it comparatively. I had it before it became popular (and was free).
On the negatives...
I don't like that Whatsapp automatically adds friends into Favourites when... nope they are not. Line does it better that way, as well as listing those with Line. Also like that I can add them as friends instead of being a default setting.
Recent update also made it rather cluttered. Prior to this update the timestamp was slightly to the side and not as obvious. Now it is rather cluttered with it at the bottom of the text sent.