I was never a fan of it and here are some of my reasons
it was a pain to skip it when an app used it.
it caused a big delay in the app start
you're limited to what they offer
you couldn't have a global leaderboard for Android & IOS (I believe it runs on IOS too for a while but I don't know if there's a B4i lib for it)
probably blocked in China
I use my own leaderboard system instead which gives me full flexibility which is ofcours limited to my own knowledge.