I'm a big fan of these objects, as they make both mining and building very interesting/easier. I do have a suggestion on how to improve them however:
Give them a short 'placement time' similar to torches/etc. I find that when I place them, if I hold the button a split-second too long, it often places another on top of the first.
As there is no way to retrieve them(currently) It leads to some wasted resources/incorrectly placed objects.
Thanks!