I backed 12 projects so far and every single one of them is late, some by as much as a year when the initial timeline was less than 6 months. I also haven't received a single thing of what I backed yet.
I like the whole Kickstarter idea but these delays and false promises will definitely make me think twice next time I want to back something. I wish people were held accountable more.
Even personalized thank you notes that were promised never made it. There's no excuse for that really...
It is probably easier for music, books etc to be delivered on time, compared to making physical products - products depend a lot on external factors (overseas manufacturers etc)