Very nice, detailed article. I used Habitica for a couple of months but as I collected more pets and got stronger somehow I lost motivation in it. I just did not feel as rewarded as before (~ monkey brain :D). Altough I have to confess, at the time I was playing it every day my life was more balanced and kind of I felt more like an adult.
I would recommend everybody to give it a shot! It is a really nice website and as mentioned above you can create guilds and play with your friends which is an awesome feature as well.