I remember that when Apple started announcing that they were new emoji's in the new iOS versions all of a sudden people updated WAY faster instead of waiting a few months.
It really does seem to be something that drives adoption.
Invisible ink is very useful. I've used it to text people minor pieces of privileged information at work when I don't know who can see their phones. After all, most people just leave their phones on table tops with notifications on. It's also great for texting with my wife when she is with her parents or traveling with co-workers.
